World War II: Military, 1941-1945

By the end of this lesson, students will be able to:

• Trace the major Allied campaigns in the European theater from the Battle of the Atlantic through Operation Torch, the Italian campaign, D-Day, and the Battle of the Bulge to the German surrender on May 8, 1945.
• Account for the role of the Eastern Front in the Allied victory in Europe, including Stalingrad as the turning point of the Soviet-German war and the disproportionate share of the German army the Soviets engaged.
• Trace the major U.S. campaigns in the Pacific theater from the Doolittle Raid through Coral Sea, Midway, Guadalcanal, the island-hopping campaign, Iwo Jima, and Okinawa to the Japanese surrender on September 2, 1945.
• Account for the decision to use atomic weapons against Hiroshima and Nagasaki and identify the principal lines of the historical debate over necessity, alternatives, and motive.
• Explain how the Holocaust unfolded in occupied Europe between 1941 and 1945 and account for the constrained Allied response, including the 1944 War Department decision against bombing Auschwitz.

The Roosevelt administration entered the war committed to a Germany-first grand strategy worked out with Winston Churchill at the Arcadia Conference in Washington in late December 1941. The reasoning was straightforward. Germany controlled industrial Europe, was the only Axis power that posed a strategic threat to the Western Hemisphere, and was carrying the war to the Soviet Union on a scale that, if the Soviets collapsed, would free the entire German army for redeployment. Japan, by contrast, was a finite naval threat that could be held with the Pacific Fleet while the main Allied effort dismantled Germany. The strategy did not mean abandoning the Pacific. It meant ranking the European theater first when shipping, aircraft, and divisions had to be allocated between fronts (KC-7.3.III.D).

The first long contest in Europe was the Battle of the Atlantic, the running fight between Allied convoys and German submarines for the shipping lanes that supplied Britain. German U-boats sank thousands of merchant ships through 1942 and into early 1943, threatening to starve Britain out of the war before any Allied land offensive could begin. The corner turned in mid-1943 when long-range patrol aircraft, escort carriers, the convoy system, and the British and U.S. code-breaking effort against the German naval Enigma combined to push U-boat losses past sustainable levels. Without that victory at sea no later operation in Europe was possible.

The first Anglo-American land offensive against the Axis came in November 1942 with Operation Torch, the landing of Allied forces under General Dwight Eisenhower on the beaches of French Morocco and Algeria. The campaign in North Africa carried Allied armies east through Tunisia, joined the British Eighth Army that had been fighting Erwin Rommel since 1940, and by May 1943 had cleared the southern shore of the Mediterranean. From North Africa the Allies leaped to Sicily in July 1943 and to the Italian mainland in September. The Italian campaign of 1943 and 1944 was a slow, costly fight up the spine of a defended peninsula. The amphibious landing at Anzio in January 1944 stalled on the beach for four months. The German line anchored on the abbey of Monte Cassino held through four Allied assaults before falling in May 1944. The Italian campaign tied down twenty German divisions that could not be moved to either France or the Eastern Front; whether that was worth the price has been argued by historians ever since (KC-7.3.III.D).

The decisive Allied effort in western Europe was the cross-channel invasion of Normandy on June 6, 1944, the operation history calls D-Day. Roughly one hundred fifty thousand American, British, Canadian, and other Allied troops landed on five beaches between Utah on the right flank and Sword on the left, supported by the largest naval armada ever assembled and by airborne divisions dropped behind German lines the previous night. The landings cost more than ten thousand Allied casualties on the first day. By late summer the Allies had broken out of the Norman bocage, liberated Paris on August 25, and pushed the Wehrmacht back to the German border. Germany's last major offensive came that December, when twenty-five divisions attacked thinly held American lines through the Ardennes forest in what became the Battle of the Bulge. The U.S. Army held at Bastogne, repelled the offensive at a cost of nineteen thousand American dead, and resumed the advance into Germany in early 1945. Soviet armies entered Berlin on April 30, Adolf Hitler took his own life that afternoon in the Fuhrer-bunker, and Germany surrendered unconditionally on May 8, 1945 (KC-7.3.III.D).

None of that was possible without the Eastern Front. The Soviet Union had borne the brunt of the European war since June 1941, when Germany broke the Molotov-Ribbentrop Pact and invaded with three million troops. Soviet forces lost more soldiers killed in 1941 than the United States lost in the entire war. The German offensive ground to a halt in front of Moscow in December 1941 and was thrown back; the second German offensive in 1942 drove for the oilfields of the Caucasus and stalled at the city of Stalingrad, where between November 1942 and February 1943 a Red Army counteroffensive surrounded the German Sixth Army and forced its surrender. Stalingrad was the turning point of the European war. From early 1943 onward the Red Army pushed German forces steadily west, fought the largest tank battle in history at Kursk in July 1943, and was inside Berlin by April 1945. Throughout the war between two and three German soldiers died on the Eastern Front for every one killed by the western Allies; American grand strategy depended on a Soviet ally most Americans never saw.

The Pacific war opened with the December 7, 1941 Japanese attack on the Pacific Fleet at Pearl Harbor and continued through six months of Japanese conquests across the Philippines, Malaya, Singapore, the Dutch East Indies, and Burma. The first American answer was symbolic. In April 1942 sixteen Army B-25 bombers under Lieutenant Colonel James Doolittle launched from the carrier Hornet, hit Tokyo, and crash-landed in China; the Doolittle Raid did almost no military damage but it raised American morale at a moment when the news from the Pacific was almost uniformly bad and it pushed the Japanese navy to seek the decisive carrier engagement that produced its defeat. Two months later, in May 1942, the carrier battle of the Coral Sea halted a Japanese advance toward Port Moresby and the supply lines to Australia. In June 1942 the carrier battle of Midway, fought entirely between aircraft launched from ships hundreds of miles apart, sank four Japanese fleet carriers and ended Japanese expansion across the central Pacific. Midway is the consensus turning point of the Pacific war (KC-7.3.III.D).

From Midway forward the United States fought the Pacific war on the offensive. The campaign for Guadalcanal in the Solomon Islands ran from August 1942 to February 1943 and cost both sides heavily; the U.S. victory denied Japan the airfield it had been building and proved that American Marines could pry a defended island away from a determined Japanese garrison. After Guadalcanal, U.S. forces advanced toward the Japanese home islands along two axes. General Douglas MacArthur commanded the Southwest Pacific Area and worked north along the New Guinea coast toward his promised return to the Philippines. Admiral Chester Nimitz commanded the central Pacific and drove west through the Gilbert, Marshall, and Mariana islands. Both lines pursued an island-hopping strategy: rather than retake every Japanese-held island, the Allies seized strategically positioned islands that could base bombers and submarines, and bypassed and isolated the rest. The strategy economized on manpower and shortened the road to Tokyo. By late 1944 American B-29s based in the Marianas were burning Japanese cities, and MacArthur had returned to the Philippines (KC-7.3.III.D).

The closing battles of the Pacific war were the bloodiest. The five-week battle for Iwo Jima in February and March 1945 produced the iconic Joe Rosenthal photograph of Marines raising the flag on Mount Suribachi and cost more than six thousand American dead and twenty thousand Japanese dead from a garrison of twenty-one thousand. The eighty-two-day battle for Okinawa, from April through June 1945, was the heaviest U.S. casualty count of the Pacific war: more than twelve thousand American killed, more than seventy thousand Japanese killed, and roughly one hundred thousand Okinawan civilians killed in the crossfire. Okinawa convinced American military planners that an invasion of the Japanese home islands, scheduled for November 1945 (Operation Olympic) and March 1946 (Operation Coronet), would cost hundreds of thousands of American casualties and millions of Japanese (KC-7.3.III.D).

Into that calculus the Manhattan Project delivered an alternative. The U.S.-British-Canadian crash program to build an atomic bomb, begun in 1942 under General Leslie Groves and the physicist J. Robert Oppenheimer, tested its first weapon at Trinity Site in New Mexico on July 16, 1945. President Harry Truman, who had succeeded the dying Roosevelt in April, approved its use. On August 6, 1945 a uranium bomb destroyed Hiroshima, killing roughly seventy thousand people instantly and tens of thousands more in the weeks and years that followed. On August 8 the Soviet Union declared war on Japan and invaded Japanese-held Manchuria. On August 9 a plutonium bomb destroyed Nagasaki. Japan announced its acceptance of unconditional surrender on August 15, and the formal surrender was signed aboard the USS Missouri in Tokyo Bay on September 2, 1945 (KC-7.3.III.D).

The historical debate over Hiroshima and Nagasaki has not closed. The traditional case for the bombings, advanced by the Truman administration in 1945 and by Henry Stimson in a 1947 article, held that the weapons forced the Japanese surrender without an invasion that would have cost hundreds of thousands of American lives and millions of Japanese. A revisionist case beginning in the 1960s asked whether Japan was already prepared to surrender on substantially the terms it eventually accepted, whether a demonstration on an uninhabited target would have sufficed, whether the Soviet declaration of war on August 8 was the more decisive shock to the Japanese government, and whether the bombs were aimed at least partly at Stalin and the Cold War balance the war was already producing. Most historians today accept that the bombings shortened the war but disagree about whether they were necessary, whether they were morally justified, and whether the Truman administration weighed the alternatives seriously enough. The debate is one of the AP exam's most reliably tested controversies (KC-7.3.III.C.ii).

Behind the European war ran a second, slower catastrophe that the Allied victory exposed. The Holocaust was the systematic, state-organized murder by Nazi Germany of roughly six million European Jews and an additional five million civilians and prisoners categorized as enemies of the regime, including Roma, people with disabilities, Soviet prisoners of war, Polish civilians, gay men, and political dissidents. The killings began with mass shootings by mobile Einsatzgruppen units behind the German front in 1941 and escalated after the January 1942 Wannsee Conference into an industrial system of ghettos, deportation by rail, and extermination camps at Auschwitz-Birkenau, Treblinka, Sobibor, Belzec, and Chelmno. The Allied response was constrained. The State Department and the British Foreign Office knew by 1942 of the systematic killings; an interagency War Refugee Board, created by Roosevelt in January 1944, helped save several hundred thousand Jews from deportation in the war's final eighteen months. In June 1944, the U.S. War Department declined a Jewish-organization request to bomb the rail lines and gas chambers at Auschwitz, arguing that aircraft were better used against military targets and that bombing the camp would risk killing prisoners. The 1945 liberation of Bergen-Belsen, Dachau, and Buchenwald, captured in U.S. Army Signal Corps photography, fixed the Holocaust at the moral center of the postwar Allied claim to victory and produced the legal framework for the Nuremberg trials of 1945 and 1946 (KC-7.3.III.A).

The accounting of the war was on a scale Americans had never seen. Roughly four hundred thousand Americans died in uniform between 1941 and 1945, more than the total of every other American war except the Civil War. Soviet dead reached eleven million soldiers and as many as fifteen million civilians. Polish dead reached six million, half of them Jewish; German dead reached four million; Japanese dead reached more than three million; Chinese dead reached at least twenty million across the long war that began with the Japanese invasion in 1937. The continental United States, almost alone among the major belligerents, came out of the war richer than it had entered, with two-thirds of the world's gold reserves, the only intact major industrial economy on earth, and a monopoly on the atomic weapon. Out of that asymmetry came the postwar order that the next lesson takes up: occupation governments in Germany and Japan, the United Nations, the Bretton Woods financial system, and the Cold War contest with the Soviet Union that organized the second half of the twentieth century (KC-7.3.III.D).

A military lesson works best when it samples sources from both theaters and from both ends of the chain of command. The four excerpts below mark the European, Pacific, atomic, and Holocaust threads of the war.

1. (Causation) Account for the Roosevelt administration's choice of a Germany-first grand strategy after Pearl Harbor. Identify two pieces of evidence in the strategic situation of December 1941 that made the choice rational, and one piece of evidence that complicated it.
2. (Comparison) Compare the war in the Pacific with the war in Europe along three axes: the geography, the size of Allied ground forces engaged, and the role of strategic bombing. What does the comparison tell you about the demands the two theaters made on the United States?
3. (Continuity and Change) Account for the role of the Eastern Front in the Allied victory in Europe. To what extent did Soviet contributions to the war shape the Cold War conflict that followed?
4. (Causation) The Truman administration ordered the use of atomic weapons against Hiroshima and Nagasaki in August 1945. Identify two arguments the administration offered at the time and two counterarguments raised by historians since. Which set do you find more persuasive, and on what grounds?
5. (Continuity and Change) Account for the constrained Allied response to the Holocaust. Identify one specific decision (for example, the 1944 War Department refusal to bomb Auschwitz) and account for the reasoning the policymakers offered at the time.

Draft alignment — pending educator review. AP USH codes correspond to the official College Board Course and Exam Description (Effective Fall 2023, Version 1). Statements below are paraphrased in the CountryReports voice; refer to the College Board's published CED for verbatim wording.