Joseph V. Micallef is a best-selling military history and world affairs author, and keynote speaker. Follow him on Twitter @JosephVMicallef.
In April 1945, with the Soviet army closing in from the East and an Anglo-American army closing in from the West, it seemed that Nazi Germany's fate was a foregone conclusion.
Within weeks, Berlin had been captured by Soviet forces, Adolf Hitler had committed suicide and, on May 7, Germany surrendered unconditionally.
The outcome of the European war, however, could have turned out very differently had Hitler been able to stage the last-ditch defense he had planned in the Bavarian Alps.
Termed the "National Redoubt," or Alpine Fortress, it was centered on Hitler's retreat in Berchtesgaden, the Berghof. It consisted of a system of defensive works in the rugged Bavarian Alps. At its center was a command complex of 200,000 square feet hollowed out in the mountain beneath Hitler's chalet. The complex was surrounded by an additional 50 buildings and was intended as an alternative headquarters for the German government to carry on the war effort if Berlin fell.
The command complex was connected by tunnels to the nearby town of Berchtesgaden and was also connected to the German rail network.
The existence of the National Redoubt was known to the Allies. The effort had been organized by Heinrich Himmler beginning in November 1943. Most of the leading Nazis had homes around Berchtesgaden.
Nazi air chief Herman Goering, for example, was captured in the area after the end of the war. Additionally, a number of trains filled with loot pillaged by the Nazis from occupied Europe were also discovered in the vicinity.
With Germany's industrial heartland occupied by U.S. and British forces, and with Berlin in the hands of Soviet forces, what would have been the point of needlessly continuing a war that Germany could not possibly win?
Hitler had longed believed that the alliance between the U.S. and Great Britain, on the one hand, and the Soviet Union on the other would ultimately fail. He was certain that the two sides would eventually find themselves in conflict over the control of Europe.
When the Allied coalition eventually collapsed, Hitler reasoned, each side would seek Nazi Germany as an ally to bolster their forces against the other party, giving the Nazis a way out from what seemed to be certain doom.
Hitler was right, both about the eventual collapse of the wartime Allied coalition and about the eventual rehabilitation of Germany, though his timing was off by about a decade. Anglo-American cooperation with the Soviet Union eventually gave way to a Cold War, beginning in 1948, that would last for a half century.
Moreover, alarmed by the strength of Soviet forces in Eastern Europe, the U.S. in 1955 successfully pushed for the inclusion of the Federal Republic of West Germany into the NATO alliance and to the creation of a half-million-strong German army.
The possibility that the defeat of Nazi Germany would trigger a new round of fighting between the Soviet Union and Anglo-American forces was an eventuality that was considered by both the Anglo-American allies and the Soviet Union.
Documents released after the collapse of the Soviet Union confirmed that Joseph Stalin had considered ordering Soviet forces to continue to push west all the way to the English Channel after the fall of Berlin -- a decision that would have brought them into conflict with U.S. and British forces.
Ultimately, Stalin demurred, believing that the rapid withdrawal of U.S. forces from Europe and the chaos precipitated by the war would allow Soviet forces to roll over the rest of Europe with little, if any, opposition.
British Prime Minister Winston Churchill also was concerned that Soviet forces would continue to advance westward following the collapse of Nazi resistance. In the spring of 1945, he ordered the Joint Planning Staff of the British Armed Forces to develop a contingency plan in the event of a surprise attack by Soviet forces in Germany. Termed Operation Unthinkable, the original plan called for repulsing the Soviet attack and then a counterattack with the objective of pushing Soviet forces back to the Vistula River.
The plan was later modified to envision a British defense of Western Europe in the event that U.S. troops were withdrawn and the Soviets mounted an invasion toward the North Sea and the Atlantic coast of France.
The British plans for Operation Unthinkable were not declassified and released until 1988. It's likely that Stalin had some knowledge of the British plans for Operation Unthinkable, as it is believed that some of the details were leaked to the Soviets by Soviet agent Guy Burgess and other members of the notorious Cambridge Five spy ring.
Some awareness of the British plans may explain why, in June 1945, Soviet Army commander Marshal Georgy Zhukov ordered Soviet troops in Poland and East Germany to regroup and adopt defensive positions.
At the heart of both Hitler's and Churchill's plans was the German Army Group C. The army group was tasked with the defense of northern Italy and occupied a region stretching from northern Italy to western Austria and southeastern Germany.
Numbering an estimated 1.3 million men, most of whom were being held in reserve, Hitler envisioned that Army Group C would provide the manpower for the defense of the National Redoubt in the Bavarian Alps.
The role of the National Redoubt and its feasibility in prolonging the war has been hotly debated. Some historians, most notably Stephen Ambrose, have dismissed the National Redoubt as a myth created by German intelligence and doubted it would have made a difference.
Nonetheless, starting in February 1945, the Allies began receiving reports that German military, government and Nazi party officials and their staff had begun relocating to the region around Berchtesgaden. That same month, the SS evacuated scientists and engineers engaged with the V-2 rocket program at the Peenemunde Army Research Center to the National Redoubt.
Himmler believed that the Nazis could hold out in the National Redoubt for five years and that, from this secure location in the Bavarian Alps, they could direct a counterinsurgency campaign against the Allies by 200,000 Nazi sympathizers.
U.S. Gen. Dwight D. Eisenhower, supreme commander of the Allied Expeditionary Force in Europe, took reports of the German strategy to hold out in the National Redoubt seriously enough to bolster Allied strength on the southeastern front to allow for a quick thrust across Bavaria and into Austria in order to cut off German troops from reinforcing the redoubt.
Concerns about the existence of a National Redoubt also influenced Eisenhower's decision to forgo advancing into Germany on a narrow front in order to seize Berlin first, as U.S. Gen. George S. Patton and British Field Marshal Bernard Montgomery had advocated, in favor of a broad advance across Germany and a thrust to the southeast across Bavaria and western Austria.
Churchill's Operation Unthinkable also relied on Army Group C, envisioning their recruitment into an Anglo-American army tasked with rolling back Soviet forces and later into a British army resisting a Soviet thrust across Western Europe.
Which brings us to Operation Sunrise. In February 1945, Waffen SS Gen. Karl Wolff sent a message to the Allies, through Swiss intelligence, that he was prepared to negotiate the surrender of Army Group C. Between February and May 1945, Wolff met with OSS agent Allen Dulles to discuss the surrender terms.
As part of the negotiations, Dulles agreed to shield Wolff from potential prosecution for war crimes. The Allies believed that Wolff had been complicit in the murder of East European Jews. Evidence that emerged later implicated him in the murder of up to 300,000 civilians, most of them East European Jews, but he was never charged with any crimes.
Wolff refused to meet with Dulles if Soviet representatives were also present. The U.S. did not inform the Soviets of the negotiations until March 16. The disclosure triggered a heated exchange of letters between U.S. President Franklin D. Roosevelt and Stalin, and Soviet claims that the U.S. was negotiating a separate peace with Nazi Germany.
In turn, it has been rumored that Wolff, who had not been authorized to conduct negotiations with the Allies, informed Berlin that he was discussing an agreement to provide safe passage to Adolf Hitler and other leading Nazis, and a possible anti-Soviet military alliance between Anglo-American forces and Nazi Germany.
It's not clear whether any of this is true. It may have been the work of Soviet propagandists trying to create a story that the Allies had considered or even begun negotiating a separate peace with the Nazis.
It also created the basis for a later Soviet claim that Hitler had escaped with Allied assistance from Berlin. Had Wolff really told his superiors that he was negotiating a military alliance with the U.S. and Great Britain, it's hard to imagine that Berlin would not have sent someone more senior to conduct the negotiations.
In any case, an instrument of surrender was signed on April 29, 1945, effective May 2. With the surrender of Army Group C, any possibility of holding out in the National Redoubt ended. The next day -- April 30, 1945 -- Hitler committed suicide, although the exact date of his death is still debated. On May 7, Karl Donitz signed the instrument of unconditional surrender on behalf of the German government.
After the war, Hitler's retreat at Berchtesgaden was bulldozed by the German government. The ruins were planted with trees, and any trace of its existence was eliminated lest the site become a shrine to the dead Nazi leader. The tunnels and command post drilled into the mountain were sealed off. Some tunnels beneath Berchtesgaden, however, have been reopened and are accessible to visitors.
It remains unclear to this day whether the Nazis' National Redoubt strategy would have succeeded in prolonging the war until the collapse of the Anglo-American-Soviet coalition. With the surrender of Army Group C, however, it was no longer a viable option. Within days of that surrender, Hitler was dead and the Nazi government had also surrendered.
The war in Europe was over, although not quite in the way the Nazis had imagined it would end.
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