An indispensable factor in Allied victory in World War II was the alliance among the major powers: the United States, Great Britain, and the Soviet Union. Fighting alone, none of the Allies could have prevailed against Nazi Germany. Together, they were able to defeat what had been the strongest military power in the world.

The major Axis nations—Germany and Japan—did almost nothing to help each other. In the Pacific, Japan fought alone against the United States and its other allies, especially Australia and China. Britain and the Soviet Union contributed relatively little to Allied efforts in the Pacific.

In Europe, Germany enjoyed the support of Hungary, Romania, Bulgaria, and Italy, but none of these nations had the resources and industrial might to field a fully modern army. The Germans conscripted tens of thousands of men from the territories they occupied as their armies swept east, but such coerced recruits made poorly motivated soldiers.

In contrast, the Allies had a single galvanizing purpose: to defeat Hitler. The United States devoted only about 15 percent of its war effort to defeat Japan; the remaining 85 percent was directed against Germany. Little else united the Allies. Political and ideological differences between the capitalist democracies and a Communist dictatorship produced suspicion and mistrust. Nonetheless, the Allies collaborated to force the unconditional surrender of Germany. Three militarily significant consequences of the wartime alliance stand out as decisive ingredients of Allied victory: American materiel support for Britain and the Soviet Union; American and British bombing campaigns and the D Day invasion of Europe; and the Red Army’s success in stopping the eastward advance of the German army at Stalingrad, then driving it back to Berlin.

The flood of military supplies that poured out of American factories during the war made Allied victory possible. In total, the United States produced two-thirds of all Allied military equipment. In addition to shipping hundreds of millions of tons of supplies to Britain and stockpiling equipment for the D Day invasion, the United States sent more than half a million military vehicles to the Soviet Union, accounting for the bulk of the Red Army’s motorized transportation. By 1944, American refineries supplied 90 percent of the Allies’ high-octane gasoline, prompting Stalin to raise a toast at the Teheran conference “to the American auto industry and the American oil industry.” American food shipments provided the equivalent of one meal a day for each Russian soldier. The American canned meat Spam was distributed so widely that Soviet troops called it “The Second Front,” a sarcastic reference to the Americans’ delay in opening a second front in western Europe.

The British and American bombing campaign against German targets in western Europe served as a crucial second-front surrogate until D Day, and it eventually allowed Allied pilots to rule the skies. The bombing campaign reduced the production of tanks, airplanes, and trucks by more than a third and diverted two-thirds of Germany’s aircraft and three-quarters of its antiaircraft weapons from supporting the infantry on the eastern front to protecting German cities from Allied air attacks. Furthermore, improvements in Allied fighter planes allowed British and American pilots to decimate the Luftwaffe. Although the German civilian population and Allied air crews suffered huge casualties as a result of the air campaign, it decisively aided the Soviets’ battle against the Germans on the eastern front.

But neither the bombing campaign nor the mountains of American supplies would have won the war if the Soviet Union had not stopped the seemingly unstoppable advance of the German Wehrmacht in the east. Within six months of Hitler’s surprise attack on the Soviet Union in June 1941, Stalin’s army had lost 4 million soldiers and nearly all its tanks and airplanes, and German armies threatened Moscow. U.S. military officials expected Stalin to capitulate within two or three months. Instead, the Red Army regrouped and managed to halt the Germans’ eastward advance by early 1943.

Reversal of the German assault required colossal sacrifices by the people of the Soviet Union. As the German army swept east during 1941, Russians frantically dismantled more than 1,500 industrial plants about to be captured by the Nazis, shipped them east of the Ural Mountains, and reassembled them there. They also built new plants and soon began producing thousands of new tanks, aircraft, and artillery to rearm the Soviet military. Through sheer hard work, the productivity of Soviet war industries more than doubled during the war. Meanwhile, food production plummeted, allowing the average Russian only one-fourth the amount of food available to the average German. Soviet casualties dwarfed the losses of the other Allies. For every American killed during the war, forty-five Soviets died. No contribution to Allied victory was more important than the monumental success of the Soviet Union on the eastern front.

Questions for Consideration

Connect to the Big Idea

How did “Rosie the Riveter” help the Allies defeat Nazi Germany?