Fantastic stuff, and likely not taken terribly seriously either by the casual reader or by any American official who happened to read the articles. Not, that is, until after the German counter-attack in the Ardennes, the Battle of the Bulge, provided a shocking demonstration of their continued ability to spring nasty surprises. Yet another in a distressingly long line of intelligence oversights—stretching back through the failure to note the defensive potential of the hedgerow country in Normandy to the blunder at Kasserine Pass during the North African campaign—this latest fiasco put the Allied intelligence community on full alert. By its very nature an inexact science, Intelligence assessment is a bit like trying to put a jigsaw puzzle together without seeing the original picture. Forced to process a mixture of scattered and imperfect information, some rumor, some planted by the enemy, some accurate, analysts try to take the bits and pieces and create a credible assessment based on an appraisal of enemy intentions and capabilities.  

Stung by the Ardennes embarrassment and fearful that they had overlooked key evidence, American and British intelligence officials in early 1945 began re-examining information, focusing on three key areas: secret weapons, guerrilla activity, and prolonged resistance in an Alpenfestung (Alpine Fortress, or National Redoubt). Of the three fears, the latter seemed most likely and threatening. Not only did the Alpine area of southern Germany, western Austria, and northern Italy, with its massive mountain ranges, narrow valleys, and winding roads, offer an ideal defensive terrain, but German forces in Italy had already demonstrated their skill at such fighting. Furthermore, the commander of the German forces in Italy that had so stymied and frustrated the Allies, Field Marshal Albert Kesselring, had just been appointed commander of all German troops in the south. In addition, Allied advantages such as superior air power and ground mobility would to a considerable extent be neutralized by the poor weather and cramped mountainous terrain. Moreover, underground factories in southern Germany were known to be producing the latest miracle weapon, jet airplanes, which might operate from airfields hidden in the mountains. Finally, the human factor could not be ignored, especially since Hitler had already issued any number of "stand and die"” orders. Headlines in the "Völkischer Beobachter", the Nazi Party newspaper, seemed to confirm such a determination to fight to the last, repeatedly proclaiming, "We will never capitulate," and "Relentless people’s war against all oppressors".

Indeed, to Churchill and others, the sustained and fanatical German resistance around Budapest and Lake Balaton in Hungary seemed pointless except as a desperate attempt to keep the eastern approaches to an Alpenfestung open for retreating German troops.  Worried about protracted resistance from a mountain stronghold, aware of the increasing imperatives of the Pacific war, and, not least, determined not to be caught off guard again, Allied intelligence officials set about assembling evidence to confirm their explanation for German actions.

Once begun, the search resulted in what appeared to be ample substantiation of the reality of an Alpenfestung. Ironically, the notion of a National Redoubt, indeed even the name, stemmed from Swiss efforts between 1940 and 1942 to construct a mountain fortress that would serve as a deterrent to any possible German attack. By late 1943, with the tide of war turning against them, the Germans began exploring the possibility of utilizing existing World War I positions in the Dolomite Alps of Northern Italy as the basis for a defensive line running east from Bregenz on Lake Constance to Klagenfurt and then along the Yugoslav border toward Hungary. Since many of these fortifications had remained in relatively good condition, the Germans assumed they could build a strong position rather quickly. Thus, it was not until September of the following year that work began on improving the southern Alpine fortifications. That same September, the Oberkommando der Wehrmacht (German Armed Forces High Command, or OKW) ordered a survey of the western and northern Alpine regions with an eye toward linking these with the southern defenses. An engineering staff under Brigadier General August Marcinkiewicz was established at Innsbruck for the purpose of mapping out future defensive positions, although no actual construction began.

As the Germans began initial preparations for construction of an Alpine fortress, intelligence agents just across the border in Switzerland took note. In late July 1944, Swiss intelligence agent Hans Hausamann sent a report to his government indicating a growing concern that fanatical Nazis would hold out in the Alps until new secret weapons or a split in the Allied coalition produced a decisive turnaround in the war. Swiss intelligence also informed Allen Dulles, the Office of Strategic Services (OSS) representative in Bern with whom it maintained regular contact, of the possibility of prolonged German resistance. Although himself somewhat skeptical, Dulles conceded that the Swiss took the possibility of a Redoubt seriously, so he dutifully dispatched this information to Washington, where it likely would have been relegated to the wild rumor file except for two coincidental developments in September. First, one of the many American intelligence agents working in Switzerland sent a detailed report to Washington informing of powerful German defenses in the Alps. He spoke of monstrous fortifications with underground factories, of weapons and munitions depots, of secret airfields and stockpiles of supplies. Should the Germans successfully retreat into this fortress, the agent warned, the war could be extended by six to eight months and American forces would suffer more casualties than at Normandy. Of equal concern, he predicted that the Nazis could hold out for two years in the event this last bastion was not assaulted, a situation which might encourage widespread guerrilla activity throughout occupied Germany.

Then, on 22 September, the Research and Analysis Branch of the OSS issued a scholarly analysis of southern Germany and its potential as a base for continuance of the war. Taken together, these reports nurtured a growing concern in Washington of the possibility of a last-ditch German defense in the south. After all, if the Swiss had created such a stronghold, it seemed only logical that the Germans could and would as well. Once conceived, the fear of an Alpine fortress exercised a strange fascination on American officials determined to avoid any further shocks like the Ardennes offensive. The Germans had certainly undertaken some type of military activity in various areas of the Alps, the idea of a Götterdämmerung struggle in a mountain aerie conformed with Hitler’s personality and previous actions, and there seemed little reason to doubt that the SS would continue to obey orders and fight fanatically. Moreover, Bavaria had been the birthplace of Nazism, and many of its leaders, not least Hitler, displayed an almost mystical attraction to the mountains. Finally, because the redoubt lay in the future American zone of occupation, it would be solely an American problem if allowed to become operational.

Unfortunately, despite the undeniable logic of American assumptions, much of the information on which their suppositions were based had been planted by SS-Sturmbannführer Hans Gontard, head of the Sicherheitsdienst (Security Service, or SD) office in the border town of Bregenz. Having intercepted the OSS report to Washington warning of the Alpenfestung Gontard could only marvel at what seemed to him boundless American gullibility. In late September, in fact, Gontard showed a copy of the report to Franz Hofer, the Gauleiter (party leader) of Tyrol, whom the OSS regarded as a radical Nazi fanatic, in order to demonstrate the ineptitude of the American intelligence service. In a grand irony, Hofer not only perceived how American fears could be exploited by propaganda, but also that the idea of a mountain fortress made sense from a military perspective. In early November, therefore, he dispatched a memorandum to Martin Bormann, head of the Nazi Party and secretary to Hitler, that detailed the need for immediate construction of a defense line in the Alps. What had not existed, what the Americans had conceptualized, Hofer now tried to make a reality. In addition to construction of fortifications, he proposed diverting enormous quantities of supplies, munitions, machinery, and military equipment to depots within the proposed fortress area, closing the region to all civilians and refugees, transferring thirty thousand Allied POWs to the Alps for use as hostages, and withdrawing the German army in Italy, still largely intact and undefeated, to the southern defense line. To Hofer’s great distress, however, no one in authority in Berlin showed interest in his suggestions, regarding them as overly pessimistic. Bormann, in fact, refused even to pass Hofer’s memorandum on to Hitler for fear, at a time when great hopes were vested in the Ardennes operation, of being characterized as a defeatist.

Only Propaganda Minister Josef Göbbels recognized the value of an Alpenfestung, and then merely to exploit "Redoubt Hysteria" among the Americans. Convening a secret meeting of German editors and journalists in early December 1944, Göbbels ensured the dissemination of rumors about a National Redoubt by expressly forbidding any mention of such a thing in German newspapers. Then, in January 1945, he organized a special propaganda section to concoct stories about Alpine defensive positions. All the stories were to stress the same themes: impregnable fortifications, vast underground storehouses loaded with supplies, subterranean factories, and elite troops willing to fight fanatically to the last. In addition, Göbbels saw to it that rumors leaked not only to neutral governments but also to German troops. Because Allied intelligence drew on POW interrogations as well as reports from neutral countries, these actions ensured the further dissemination of apparent evidence of the existence of an Alpenfestung. Finally, Göbbels enlisted the aid of the SD to produce fake blueprints, reports on construction timetables, and plans for future transfers of troops and armaments into the redoubt.

Aided by the efforts of Göbbels’s team, American journalists seized the tantalizing story. In late January, Austrian-born Erwin Lessner reported in a sensational article in "Colliers" on an elaborate guerrilla warfare school being run near Berchtesgaden. There, elite SS and Hitler Youth members were allegedly being instructed in partisan warfare, with the goal of harassing the conquerors and terrorizing any Germans co-operating in the occupation. Lessner emphasized that these young guerrillas, given the name Werewolves, would stage lightning raids out of an Alpine fortress, trying to inflict as much damage and as many casualties as possible before retiring back to their mountain citadel. Although confident that this guerrilla war would ultimately fail, Lessner warned that it could nonetheless cause grave difficulties if not taken seriously by the Allies. After all, he pointed out, the Nazis had the advantage of having studied all of the resistance movements that had opposed their rule, and so had a clear understanding of how to conduct an effective underground war. In Lessner’s assessment, the Nazis meant guerrilla war to be another V-weapon, which, after all, in German stood for Vergeltung (revenge, retaliation). The goal, then, was not victory as much as it was vengeance.

A few days later the Swiss added fuel to the smoldering fire. The Zürich newspaper "Weltwoche", under the headline “Festung Berchtesgaden,” reported on 2 February 1945 that "reliable reports out of Germany contained technical details of the construction of a Berchtesgaden Redoubt position with the Obersalzburg as the nerve center". As the nearest neighbors to Germany, the Swiss had instant credibility, which was reinforced in the article by the accumulation of detail about the alleged mountain fortress. Running along the rugged crest of the mountains, the defensive system, with its installations of machine gun nests, anti-aircraft positions, radio transmitters, and secure Bunkers at the passes provide evidence that the romantic dream [of sustained resistance] is taken seriously and that good German thoroughness is once again being directed at a fantastic goal. . . . In the heights around the Königssee, in the old salt mines in the area, in hollowed out mountains and along valley roads, little by little massive depots of war material, munitions, repair and maintenance shops are being established. Industrial facilities to produce war material are being built there. Airplane factories for jet fighters are being erected, huge fuel depots put in place. . . . Underground airfields and hangers stand ready. . . . Grain and potato 'Endkampf' supplies have been gathered. "The fortress Berchtesgaden," the article emphasized, "is no legend," with its political purpose more important than its military significance. It was, the author declared, intended to keep alive "a bacterial culture of National Socialist ideology and strength" until the day when a renewed Nazism would again seize power.

Little over a week after the ""article, a long piece in the "New York Times Magazine", 'Last Fortress of the Nazis,' seemingly confirmed the Swiss assertion. The author, Victor Schiff, almost certainly had read the Swiss article, for much of his detail mirrored the information contained in the Zürich newspaper. Schiff asserted that the Nazis, having nothing to lose, would fight bitterly to the last in the hope of a reversal of fortune, and that the fight would be carried on by Hitler’s fanatical elite, the SS. He went on alarmingly:

"It is noteworthy that since the beginning of the Russian offensive very little has been heard of the SS troops on the Eastern Front. . . . It looks as if the Wehrmacht and Volkssturm are being deliberately sacrificed in rear-guard actions. . . . SS formations are likely to retreat swiftly southward to a region already selected as the last theater of operations in Europe. . . . It will stretch from the eastern tip of Lake Constance to the approaches of Graz in Styria . . . , [with] an approximate length of 280 miles and an average width of 100 miles, and a total area slightly larger than Switzerland. . . . It would be comparatively easy to defend this 'fortress' for a very long time with some twenty divisions . . . behind the formidable barrier of the gigantic chain of central and eastern Alps. . . . The few gaps in the valleys . . . can be sealed with more fortifications and pill-boxes dug in the rocks, and [there is] little doubt that the Todt Organization is already being used to the limit for that purpose. . . . We can assume that the Nazi High Command has started hoarding reserves of arms, munitions, oil, food, and textiles in a series of underground depots within the Alpine quadrangle".

Pointing to the difficulty posed by such an Alpine fortress, Schiff observed, "If they succeeded in holding out till the autumn of 1945, operations would have to come to a standstill till the spring of 1946 . . . [because of] the impossibility of any real warfare in such regions during the winter". Ending his gloomy assessment, Schiff raised the specter of "a monstrous blackmail," noting, "Since D-Day all the main political hostages from Allied countries have been moved by the Gestapo [German secret police] from various parts of the Reich into this Alps quadrangle". Nor could this article be dismissed as wild speculation, for Dr. Paul Schmidt, spokesman of the German Foreign Office, gave a speech on 13 February to foreign correspondents in which he boasted, "Millions of us will wage guerrilla warfare; every German before he dies will try to take five or ten enemies with him to the grave.". As another journalist, Curt Riess, argued, such talk played to the element of Todesverlangen (longing for death) allegedly rampant in German culture. Just as Wagner portrayed the world’s end as a "Twilight of the Gods,” so Hitler and Göbbels wanted their own 'Götterdämmerung 'and hoped to convince average Germans that their death was a "fate full of meaning".

By the end of the month, even the Soviets had gotten in on the action, warning in "Pravda" that the Nazis had made complete preparations for setting up "underground terrorist organizations" for the purpose of sabotage and revenge. Adding weight to these assertions, Dulles communicated his growing concern to Washington, stressing on 22 January that "The information we get here locally seems to tend more and more to the theory of a Nazi withdrawal into the Austrian and Bavarian Alps, with the idea of making a last stand there". A few weeks later, in fact, Dulles raised the possibility of not one, but several Redoubts, asserting, "When organized German military resistance collapses, there will probably be more than one ‘reduit’ or inner fortress of Nazi resistance. . . . It seems generally accepted now that a delayed defense fortress will lie in the Bavarian and Austrian Alps. Swiss sources have information which they consider reliable that substantial amounts of foodstuffs being collected here, and that some underground factories are being prepared to supply arms for mountain warfare". The problem, Dulles admitted, was that "it is impossible to put your finger on the particular area where the foodstuffs are being collected, or where these underground factories are being prepared". He then closed his dispatch with a horror scenario outlined by the "National Zeitung" of Basel: "The most important centers of resistance . . . are to be in Thüringen, south of Stuttgart, and in Middle Bavaria and Austria. There is plenty of protection there by mountains and hills, and many fortifications have been constructed. There is already an armament industry in operation. . . . The idea of [guerrilla warfare] existed in 1918. . . . Similar plans are now to be carried into effect by the Nazis, with their habitual thoroughness, and aided by their experiences with the resistance movements in occupied countries. . . . There are special schools for recruits . . . [and] huge underground ammunition plants and tremendous stores of ammunition and food".

As influential journalists and intelligence operatives supplied seemingly detailed and knowledgeable accounts of the likelihood of endless conflict in a mountain bastion, higher-ranking Allied intelligence officials too began to fall under its apocalyptic spell. The fear that thousands of GIs would be killed in subduing an Alpine fortress was a nightmare that had to be taken seriously. Increasingly, then, all military measures of the Germans came to be viewed through the lens of the apparent reality of an Alpenfestung. The continued fighting in Hungary now seemed to make sense only in relation to buying time for an occupation of the Redoubt. In addition, the numerous trains heading to the south (most, ironically, carrying looted art treasures to safety) were interpreted as military supplies heading to the fortress area. Scattered rumors gleaned from POW interrogations that referred to mysterious SS movements, bombproof buildings in mountain regions that would serve as military headquarters for a guerrilla war, and underground production facilities all added to the emerging picture of a National Redoubt. Even the missing SS divisions added to the weight of evidence pointing to a last-ditch resistance, since Allied intelligence had also noticed an absence of several key SS units before the Ardennes offensive. "Not enough weight is given the many reports of the probable Nazi last stand in the Bavarian Alps," concluded a counterintelligence assessment issued by the War Department on 12 February: "The Nazi myth which is important . . . [to] men like Hitler requires a Gotterdammerung".

In closing, the memo urged that American commanders "down to the corps level" be alerted to the danger.

A month later, Dulles seconded this contention, noting that "present [German] military strategy seems to be built around the idea of a reduit". Not to be outdone, the Research and Analysis Branch of the OSS issued a long report on 22 February summarizing much of the accumulating evidence from POW interrogations regarding an Alpine redoubt. Taking as a given the existence of an "inner bastion," the OSS stressed that it was an ideal gathering point for all retreating German forces. Psychological factors also pointed toward a drawn-out resistance. "Comprising as it does the Obersalzburg, the holy of holies among Nazi sanctuaries," the authors emphasized, "the [Alpine] region has a romantic appeal to potential last ditch heroes". The report then detailed the myriad activities throughout the region that supported the notion of an Alpenfestung: movement of SS troops and forced laborers, construction of fortifications, road and rail improvements, construction of barracks, warehouses, and weapons depots, installation of communication facilities, and excavation of tunnels. Taken together with evidence that the greatest efforts were in the Berchtesgaden area, the OSS could only conclude that the Nazis were concentrating their last resources for a defense of a National Redoubt. Continued reports from prisoner interrogations over the next few weeks seemingly confirmed this assessment, as POWs spoke of underground barracks and armaments factories, movements of SS troops, removal of civilians from specific areas, and preparation of bridges and tunnels for demolition. Finally, Allied intelligence took particular note of the activities of Organization Todt, which had specialized in erecting defensive fortifications throughout Nazi-occupied Europe. As such, they had developed a system of standardized fabrication that allowed for the rapid construction of various types of reinforced concrete structures. Moreover, sufficient labor existed in the form of forced laborers and concentration camp prisoners to expedite any last-minute construction orders.

Adding to the growing Allied fear was a mid-February report obtained by an OSS agent from neutral military attachés in Berlin that warned that the Nazis were preparing to conduct a bitter struggle from an Alpenfestung. "Military strong points are connected with each other by underground railroads," asserted the attachés.

"They have sufficient supplies for many months, the best weapons, and almost the entire German stockpile of poison gas. All people engaged in the construction of these secret facilities are to be killed, including any remaining civilians, at the beginning of the battle".

Since this report emanated from the heart of the crumbling Nazi empire, the OSS believed it could not be discounted, despite its sensationalist message and failure to address actual military possibilities. Nor could its claims of vast underground works be easily dismissed, for the Allies knew that the Germans had already moved many armaments factories into subterranean locations, which remained both undetected and undisturbed by Allied bombing. Peering into the unknown, worried about the possibility of yet another German surprise, Allied leaders increasingly agreed that the Alpenfestung was likely a reality.

Allen Dulles noted in mid- and late March the likelihood that the fierce German resistance in the Ruhr and Berlin was aimed at gaining time to gather forces in the redoubt. He then stressed:

"[Nazi leaders] now feel themselves as beyond the law. . . . We know that no fighters are more dangerous than those who fight with the energy of despair. They shrink from nothing . . . , for they have nothing more to lose".

According to Major General Kenneth Strong, the head of intelligence at Supreme Headquarters Allied Expeditionary Force (SHAEF), by March 1945 his office was "receiving a continuous flow of reports that the Nazis intended to stage a final prolonged resistance" from a National Redoubt. Strong admitted that the "reports of deep dugouts, secret hiding-places, underground factories, and bombproof headquarters were confusing and unconvincing. No single piece of information could be confirmed". An Alpine stronghold "might not be there," he concluded, "but . . . we nevertheless had to take steps to prevent it from being established. After the Ardennes, I was taking no more chances". Echoed Dulles from Bern:

"I have reported several times about the alleged plans of the Germans to establish a maquis or reduit. . . . On the whole I am inclined to believe in this possibility, but I must admit that a critical analysis of reliable data received so far does not indicate that the preparations have as yet progressed very far. There are a number of newspaper articles on the subject, with maps indicating the boundaries of the reduit and generalities about great hidden stores of provisions, about the preparation of underground factories, and the like. Much of this is probably fiction. . . . Some plants have been moved into the mountains. . . . Some preparations have undoubtedly been made, but not yet on the scale we have been led to believe. . . . [The Germans] have neither the supplies, the transport or the men to spare [for] any great effort to fortify and stock a vast inner fortress. And, from the practical angle, the talk of building in the mountains great new underground factories is nonsense. It would take years. There are some tunnels . . . which can be used and adapted. But new construction on a great scale . . . has been out of the question".

Still, he hedged:

"This does not mean . . . that we will not have to fight the Nazis into mountain retreats. It is likely that we will have to do so".

And here he added a point important to military planners:

"Nature itself, without much preparation, as the Italian campaign has shown, may make the going slow, difficult, and costly. . . . Much in the way of supplies and manpower may possibly be flung into this area at the last moment, unless our armies can cut off the Nazi retreat".

In late March he returned to this theme, stressing:

"Elaborate fortifications are not in themselves necessary to make a mountain area . . . a formidable fortress if defended by resolute men . . . [willing] to make a determined stand".

As Allied intelligence officials struggled to gain a clear picture of German intentions, they sought to supplement their sketchy knowledge with information obtained from other channels. The SHAEF "Weekly Intelligence Summary" for the week ending 11 March, for example, worried that "the main trend of German defense policy does seem directed primarily to the safeguarding of the alpine zone," and emphasized that both ground reports and limited photo reconnaissance evidence of some twenty sites indicated the likelihood of German plans for resistance in the Alps:

"Defended both by nature and by the most efficient secret weapons yet invented, the powers that have hitherto guided Germany will survive to organize her resurrection. Here armaments will be manufactured in bombproof factories, food and equipment will be stored in vast underground caverns and specially selected corps of young men will be trained in guerrilla warfare, so that a whole underground army can be fitted and directed to liberate Germany from the occupying forces. . . . It thus appears that ground reports of extensive preparations for the accommodation of the German Maquis-to-be are not unfounded".

In closing, the intelligence summary claimed that "considerable numbers of SS and specially chosen units are being systematically withdrawn to Austria; that a definite allocation of each day’s production of food, equipment, and armaments is sent there . . . ; [and] that some of the most important ministries and personalities of the Nazi regime are already established in the Redoubt area".

Immediately following the release of this report, SHAEF ordered an increase in photo reconnaissance over the suspected redoubt area. As with most of the accumulating evidence, aerial observations seemed either to confirm, or at least not to contradict, the emerging picture of an Alpine bastion. Although intelligence officials were troubled by the lack of any clear pattern to Nazi construction activity and the absence of any indication of a deliberate German move to man an Alpine fortress, aerial photographs did show a disturbing increase in the number of antiaircraft sites and weapons around Berchtesgaden.

In his official postwar report, Eisenhower admitted:

"Although there was no evidence of any completed system of defenses . . . air reconnaissance . . . revealed underground construction activity. . . . It was believed that some subterranean factories had been established in the area".

In addition, ULTRA decrypts indicated the movement in late February and early March of German military headquarters to the south. Adding another piece to the emerging puzzle, British intelligence decoded a mid-March Japanese diplomatic message from Bern, Switzerland, that reported, “considerable stocks of war material were being accumulated in two last battlegrounds, or redoubts.”

Although British intelligence generally remained more skeptical about the German ability at this late stage of the war to outfit and equip an Alpine bastion, Churchill nonetheless admitted that the possibility of such a Redoubt needed to be investigated. By mid-March, then, the Alpenfestung had advanced from a speculative secondary issue to one that now began to influence Allied strategy. No further confirmation of that was needed than one look at the giant map that hung in Eisenhower’s headquarters bearing the legend 'Reported National Redoubt'. Daily, it seemed, red marks, each representing some kind of defense installation, sprouted on the map like a fever rash. Troop concentrations and jagged lines of defensive fortifications; food, ammunition, fuel, and poison gas dumps; power stations; barracks and headquarters; bombproof underground factories—each day more symbols were added, until the map was awash with red dots. Although uneasy that most were also labeled "unconfirmed," Intelligence officers at SHAEF, stung by their earlier failures, now overreacted. To them, the forbidding mountain terrain of southern Germany and Austria seemed the greatest remaining threat in Europe, a nearly impregnable mountain stronghold that might prolong the war by months or even years. Despite a sober analysis by the Psychological Warfare Division at the end of February that regarded the whole notion of an Alpenfestung as a dubious product of Nazi propaganda, and which also emphasized German deficiencies in food, munitions, and fighting power, American intelligence officers in particular had succumbed to Redoubt fever.

In early March, both Bradley’s Twelfth Army Group and SHAEF’s Joint Intelligence Committee issued summaries that stressed the likelihood of fanatical resistance in the Alps, both to obstruct Allied occupation of south Germany and lay the basis among the young generation of a future myth that National Socialism had never capitulated. Moreover, as late as mid-April both continued to note disturbing facts, such as long lines of rail and highway traffic moving toward Berchtesgaden and the concentration of two-thirds to three-quarters of German SS and armored divisions in the south. OSS reports also seemed to confirm the assessment of the military intelligence officers.

Dulles reported on 6 April:

"While we believe that press [sic] has somewhat exaggerated extent of German preparations and probable territorial extent of reduit, there is evidence that considerable activity has recently developed . . . and that sufficient supplies and weapons have been stored . . . to equip with light arms and feed approximately 25,000 men for period of [one] year. Work on defense of important passes into reduit and on certain underground plants . . . and hidden depots has also been pushed".”In a telegram the next day, Dulles concluded, "Reduit becoming a reality. Large quantities of supplies are being accumulated. . . . Further indications are that OKW is being transferred. . . . Weissenberger [head of Wehrkreis (military district) XIII] is ardent Nazi and must be expected to fight to end".

By 21 March, the threat had led some American commanders, Bradley among them, to rethink operational goals. In a memorandum entitled "Reorientation of Strategy," the G-2 of Twelfth Army Group noted the continued German will to resist even after losing areas vital to military production. Further, the G-2 emphasized that "all indications suggest that the enemy’s political and military directorate is already in the process of displacing to the Redoubt in lower Bavaria".

Since Twelfth Army Group’s G-2 also observed a change in German defensive tactics, giving priority to the utilization of obstacles, followed by concealment, cover, fire, and movement, all of which suggested a trend toward guerilla warfare, the inescapable conclusion seemed to be that the Germans were slowly withdrawing into a prepared fortress area. As a result, Allied strategy needed to be adjusted accordingly. Bradley now proposed that instead of thrusting toward Berlin, American forces should first split Germany in two in order to "prevent German forces from withdrawing . . . into the Redoubt," then pivot south to eliminate any remaining enemy resistance. Although based on a misassessment of Nazi intentions and capabilities, this analysis nonetheless correctly noted a variety of developments and put forward a reasonable reaction to changed circumstances. In contrast, a report issued a few days later by the G-2 of General Alexander Patch’s Seventh Army, which would do the bulk of the fighting in the Redoubt area, was frankly alarmist. Colonel William Quinn, who suffered from a particularly acute case of Redoubt psychosis, issued an assessment on 25 March entitled 'Study of the German National Redoubt,' in which he expected the Germans to continue their stubborn resistance along the Seventh Army’s front and slowly retire to the Alps as a last stand. Quinn concluded that the defensible nature of the Alpine region, the fact that troops from the eastern, western, and Italian fronts could all converge on the area, and the continued German resistance in the Balkans and Italy all pointed to the existence of an Alpine fortress. He also asserted that information from "fairly reliable sources" indicated that the Germans had stockpiled weapons for 200,000–300,000 elite Nazi troops, who would fight to the last under the leadership of Hitler and Himmler. Already, he claimed, "three to five very long [armament] trains" had arrived each week since early February from the Skoda works bearing new types of weapons. Further, elaborate underground munitions factories were being built, an aircraft plant capable of producing Messerschmitts was already in operation, hydroelectric plants were generating power, and giant depots containing foodstuffs had been established in the Salzburg area.

Quinn proposed four scenarios for the expected German resistance:

(1) an immediate retreat into the Redoubt under cover of dispensable Wehrmacht units,
(2) a planned retreat in stages,
(3) defense of the outer reaches of the Redoubt and an orderly withdrawal under pressure from Allied forces, and
(4) defense of every piece of German soil to the last man.

Of the possibilities, Quinn considered the third most likely, with German forces in the west holding tenaciously to the Steigerwald, the forested peaks along the Main River, and the Franconian Heights farther to the south, then pivoting on the Black Forest and Swabian Alps as they slowly withdrew to the south. This would allow maximum numbers of German forces to reach the Alpenfestung, which Quinn had no doubt would be defended, since the Nazi leadership still had the will to resist.

Although a massive misreading of German capabilities, Quinn’s report seemed to gain legitimacy from other sources. The intelligence chief of the First French Army, part of the Sixth Army Group, issued a study that confirmed Quinn’s fears of the potential for an extended Alpine resistance. Recycling all the usual rumors, the French concluded that the reports of underground factories, storage depots, power plants, and synthetic fuel installations, in conjunction with the movement of prominent foreign hostages south, could only mean a Nazi intention to carry on the war from a mountain bastion. Despite the fact that his own G-2, General Eugene Harrison, doubted the veracity of the French report, General Jacob Devers, commander of the Sixth Army Group, passed it on to higher headquarters. At SHAEF, meanwhile, further ULTRA decrypts breathed more life into the Redoubt. A series of Führer directives in late March, especially one ordering all units of the Ersatz (Replacement) Army, except those that were "pure German" units, to be placed in "rearward positions in order to support the front [in creating a] strategic zone in depth on the eastern and western fronts," seemed to substantiate fears of a transfer of elite German units to the Redoubt. So, too, did intercepts which indicated that SS units were being moved to the south, along with high-level military headquarters staff and civilian ministries. From the sheer volume of ULTRA intercepts, it appeared in late March that a Redoubt was prepared and the Germans were moving to occupy it.

There were some in the intelligence community who, while conceding that the Germans might have theoretical plans for a mountain fortress, doubted that the enemy had the actual ability to man or defend it. Nevertheless, many of these same skeptics also admitted that, given the inconclusive and indeterminate nature of the available information, the Allies should act as though the Alpenfestung existed.

Not until 18 April, for example, did Dulles express forceful doubts about the reality of the Redoubt. Even then he raised concern over the large number of German forces, totaling well over two hundred thousand in northern Italy alone, in addition to those fighting near Vienna and in Bavaria, which might conceivably retire into the Alps and their consequent ability to hold "this difficult mountain area for some time, assuming, as we believe to be the case, that a reasonable supply of munitions and other military supplies and food have been collected there". Three days later, though, he hedged again, saying, "Reduit is to be taken seriously but will contain so many unreliable elements that will [sic] not hold out for long. . . . Military preparations within reduit feverishly but ineffectively prepared".

Then, on 25 April, Dulles reported cryptically: "OKW, Himmler ordered northern reduit front be held," which seemed again to provide evidence that the Alpenfestung was real. In addition, faced with stiffening German opposition along the eastern front, the Soviet leader Josef Stalin weighed in with his belief that the enemy would conduct a last-ditch resistance from a mountain stronghold in western Czechoslovakia, Austria, and Bavaria.

Referring to rumors of secret negotiations in Italy, Stalin in the strongest terms also expressed his fear that the western Allies might be colluding with the Germans to halt the fighting in the west and continue it in the east, with enemy utilization of a mountain Redoubt the key to the strategy.

That the Allies were aware of fairly strong German mobile reserves in Czechoslovakia added to their anxiety, as did the knowledge that arduous fighting would result if even a fraction of the troops withdrawing from Italy, the Balkans, and southern Germany reached the Redoubt area. Moreover, the Allies had no specially prepared troops for guerrilla warfare in the mountains, and in any case wanted to avoid any prolonged fighting, for—in the words of General Walter Bedell Smith, Eisenhower’s chief of staff at SHAEF—there was "a hell of a lot of pressure" from Washington to redeploy troops to the Pacific. As General Omar Bradley remarked after the war, "This legend of the Redoubt was too ominous a threat to be ignored and in consequence it shaped our tactical thinking during the closing weeks of the war". Eisenhower, further supported in his conviction by a message from General George Marshall, now acted to prevent the specter of an Alpenfestung from becoming reality. On the chill afternoon of 28 March , he composed three messages, the first of which was most significant and unprecedented. For the first time, and in order to co-ordinate the movements of the two powerful converging armies, Eisenhower communicated directly with Stalin. In his cable, he not only inquired of Stalin’s plans, but revealed his own intention not to drive toward Berlin but to move forces to the south and southeast, "thereby preventing the consolidation of German resistance in a Redoubt in southern Germany". Eisenhower then dispatched messages to Generals Marshall and Montgomery informing them of his decision and emphasizing again the "importance of forestalling the possibilities of the enemy forming organized resistance areas" either in the Alps or in Norway.

British leaders reacted angrily to Eisenhower’s actions, in part because they had not been consulted, partly because they thought the Americans failed to appreciate the political goals of the war, and also because British intelligence officials were less impressed by the possibility of the Redoubt’s existence. Despite their often caustic and acerbic remarks, though, Eisenhower’s decision was not based on a whim but, as his subsequent dispatches to Marshall, Churchill, Montgomery, and the Combined Chiefs of Staff illustrate, was grounded in a sober strategic appraisal of the situation in late March 1945.

Although his messages to Churchill, Montgomery, and the Combined Chiefs were terse and correct, the legendary Eisenhower temper revealed itself in the lengthy cable he sent to Marshall, in which he vented his fury at British condemnation of his action. “I am completely in the dark as to what the protests concerning ‘procedure’ involve,” he complained to the U.S. chief of staff: "I have been instructed to deal directly with the Russians concerning military coordination".

In defending his strategic decision to turn away from Berlin, Eisenhower noted irritably:

"Even cursory examination of the decisive direction for this thrust . . . shows that the principal effort should under existing circumstances be toward the Leipzig region, in which area is concentrated the greater part of the remaining German industrial capacity, and to which area the German ministries are believed to be moving. . . . Merely following the principle that [British Chief of Staff] Field Marshall Brooke has always shouted to me, I am determined to concentrate on one major thrust".

Eisenhower also left no doubt of his disdain for British arguments advocating a "northern thrust" toward Berlin. Not only was "Berlin itself . . . no longer a particularly important objective," but, he observed caustically, "the so-called ‘good ground’ in northern Germany is not really good at this time of year. That region is not only cut up with waterways, but in it the ground during this time of year is very wet and not so favorable for rapid movement. . . . Moreover, if, as we expect, the German continues the widespread destruction of bridges, experience has shown that it is better to advance across the headwaters than to be faced by the main streams".

Barely containing his anger, Eisenhower then noted:

"The Prime Minister and his Chiefs of Staff opposed ‘ANVIL’; they opposed my idea that the German should be destroyed west of the Rhine . . . ; and they insisted that the route leading northeastward from Frankfurt would involve us merely in slow, rough-country fighting. Now they apparently want me to turn aside on operations in which would be involved many thousands of troops before the German forces are fully defeated. I submit that these things are studied daily and hourly by me and my advisors and that we are animated by one single thought which is the early winning of this war".

Nor did the Supreme Commander leave any doubt as to how he believed that aim could best be realized, concluding his cable to Marshall: "I will thrust columns southeastward . . . in the Danube Valley and prevent the establishment of a Nazi fortress in southern Germany".

Although unspoken at the time, years later Eisenhower acknowledged another reason for his decision to opt for a southern advance over a northern one. In an interview with Cornelius Ryan, Eisenhower stressed:

"Montgomery had become so personal in his efforts to make sure that the Americans . . . got no credit, that, in fact, we hardly had anything to do with the war, that I finally stopped talking to him".

Moreover, as SHAEF’s deputy chief of staff, British lieutenant general Sir Frederick Morgan, put it: "At that moment Monty was the last person Ike would have chosen for a drive on Berlin—Monty would have needed at least six months to prepare".

Echoing this sentiment was British major general John Whiteley, SHAEF’s deputy operations chief, who noted that "the feeling was that if anything had to be done quickly, don’t give it to Monty". In his 31 March cable to Montgomery, Eisenhower had underscored this final point. "My purpose," he emphasized, "is to destroy the enemy’s forces and his powers to resist". Left unsaid was his belief that Montgomery could do neither quickly.

That the Alpenfestung existed only as a myth, as a refuge rather than a Redoubt, did not become apparent until weeks later. Although Eisenhower’s decision might now seem hasty and ill-advised, given what was known at the time of both the overall military situation and Nazi tendencies, his determination to prevent a prolonged guerrilla war appears prudent. In a cable to Marshall on 7 April, for example, Eisenhower noted a growing problem:

"In our advance into Germany we are experiencing the same thing that always happens in an invasion of enemy territory, namely, the need to drop off fighting units to protect the rear and to preserve order among the population. This task is becoming particularly acute because of the habit of displaced persons, released by our advances, to begin rioting against their ex-masters. Because of this drain on our forces we must economize everywhere if we are to maintain the vigor and strength of our planned offensives".

And maintaining vigor seemed especially important (as Eisenhower stressed in another message to Marshall later that day) in order "to disrupt any German effort to establish a fortress in the southern mountains". A week later, in a cable to the Combined Chiefs of Staff, the Supreme Commander still worried that "present evidence indicates that the Germans intend with every means in their power to prolong their resistance to the bitter end in the most inaccessible areas . . . which their troops still occupy. . . . [O]perations against certain of them . . . may involve considerable forces and also may last for some time. . . . [T]he storming of the final citadels of Nazi resistance way well call for acts of endurance and heroism on the part of the forces engaged comparable to the peak battles of the war". Significantly, Eisenhower also indicated his appreciation of "the urgent necessity for the early release of forces . . . for the prosecution of the war against Japan".

With the latter in mind, Eisenhower later on 14 April dispatched another message to the Combined Chiefs in which he stressed that "to reduce the length of time for which the enemy may prolong hostilities" it was necessary to "capture . . . those areas where he might form a last stand effectively. . . . The capability of enemy forces in the south to resist will be greatly reduced by a thrust to join the Russians. . . . However, the national Redoubt could even then remain in being, and it must be our aim to break into it rapidly before the enemy has an opportunity to man it and organize its defense fully". Eisenhower’s greatest fear, as he noted in a cable to Marshall, also on 14 April , was that "operations in the winter would be extremely difficult in the National Redoubt". Nor was the Supreme Commander alone in his fears. Influential journalists, such as Drew Middleton and Hanson Baldwin of the "New York Times", continued throughout April to warn of serious military and political problems from Nazi diehards determined to resist to the death in the National Redoubt.

The twin ironies of Allied Redoubt psychosis, as expressed in March and April 1945, were that Allied military officials were thinking more like the Nazis than the Nazis themselves, and that they mistook the logical consequences of the military attempt to split Germany in two for a deliberate Nazi decision to wage a partisan war from an Alpine fortress. In any case, without the determined American movement to the south, German military leaders might well have sought belatedly to make a virtue of necessity and turn the Redoubt into a reality. Hitler had, in fact, planned to leave Berlin for Berchtesgaden. Not until late April did he decide to stay and die in the ruins of the German capital.

In driving south-eastward to the Alps, the U.S. Seventh Army and the French First Army together took some six hundred thousand prisoners from mid April to the end of the month, a total much greater than their own combined combat strengths. It thus seemed impossible that any sizeable number of German troops had reached the Alpenfestung. When asked on 5 May at the surrender ceremony the number of Germans cut off in the Alps, the German emissary for Army Group G, Lieutenant General Hermann Förtsch, astounded General Jacob Devers, commander of the Sixth Army Group, when he indicated at least 250,000 and as many as 350,000 in an assortment of remnants, with the higher figure more nearly correct.

In addition, the Seventh Army bagged prominent military figures such as Field Marshals Albert Kesselring, Gerd von Rundstedt, Wilhelm List, and Wilhelm Ritter von Leeb, as well as political luminaries of the Nazi state such as Robert Ley, Julius Streicher, and Ernst Kaltenbrunner, the latter the head of the Reichssicherheitshauptamt (Reich Main Security Office, or RSHA), all of which seemed to add credence to the possibility of a Redoubt. Moreover, SS troops under the command of General Gotlieb Berger, which included General Max Simon’s Thirteenth SS-Army Corps with its remnants of the Seventeenth SS, Thirty-fifth SS, and Second Gebirgsdivision (mountain division), did not surrender until two days later. Although disorganized, weary, and short of food, munitions, and supplies, the total bag of more than nine hundred thousand prisoners since mid-April impressed American military officials as much for what might have been as for the absence of any Redoubt.

If British displeasure failed to recognize Eisenhower’s reluctance to incur what he saw as needless casualties or his moral repugnance at the useless destruction produced by hopeless German resistance, they also overlooked his fear that prolonged fighting in Europe would have a negative impact on both the Pacific theater as well as the grand alliance. At this late stage of the war, Hitler could only hope to buy time, but given the prospect of new German secret weapons and the growing tensions in the Allied coalition, any delay in defeating Germany raised the prospect that Hitler might be able to secure more advantageous peace terms.. In the end, then, Eisenhower’s aim was simple and straightforward—to destroy the German forces completely in the shortest possible time. Preventing any German retreat to the Alpenfestung had become his primary concern.

These illusions came to an embarrassing end in late April, when three German soldiers crossed the Elbe near Magdeburg and surrendered to the Allies, one of which was Lieutenant-General Kurt Dittmar. When asked about the Alpine Redoubt at his debriefing, Dittmar laughed and called it "...a romantic dream. It's a myth". Although initially sceptical, SHAEF soon came to accept the truth of his words.

Meanwhile, Stalin steamrollered his way towards Berlin.