World War Two: The War That Made America the Dominant Power on Earth

When the Japanese attack on Pearl Harbor brought the United States into World War Two on December 7, 1941, America was militarily unprepared but industrially positioned to become the most powerful belligerent the war would see. The scale of what followed — the mobilization of an economy, the training of an army, the production of ships and planes and tanks and ammunition on a scale that dwarfed what any other nation could manage — was the most consequential episode in American history since the Civil War.

The numbers are almost impossible to absorb. During the war, the United States produced 300,000 military aircraft, 86,000 tanks, 6,500 naval vessels, 15 million rifles, and two million trucks. The country that had 174,000 active military personnel in 1939 had sixteen million in uniform by 1945. GDP doubled between 1939 and 1945. Unemployment, which had stubbornly resisted the New Deal's best efforts, essentially vanished as every available worker was absorbed into war production.

Roosevelt had called the United States the arsenal of democracy even before Pearl Harbor, while the country was still technically neutral but supplying Britain and the Soviet Union through Lend-Lease. The phrase proved accurate. American industrial production was the decisive factor in the Allied victory, supplying not only American forces but equipping the Soviets and sustaining the British at critical moments.

The war was fought on two fronts. In Europe, the path ran through North Africa, Sicily, Italy, Normandy, and finally Germany itself. In the Pacific, it ran through Guadalcanal, Tarawa, Iwo Jima, Okinawa — island by island, at enormous cost. The war in the Pacific ended with two atomic bombs dropped on Hiroshima and Nagasaki in August 1945. The decision to use them remains one of the most debated in history. Their effects — approximately 200,000 immediate and subsequent deaths — were horrific. Japan surrendered within days.

When the war ended, the United States emerged in a position of global dominance unlike anything in history. Its homeland was entirely undamaged. Its economy was larger than it had ever been, accounting for roughly half of world GDP. Its military was the most powerful on earth. It had the atomic bomb, which it alone possessed. Every other major power — Britain, France, Germany, Japan, China, the Soviet Union — had been devastated.

America had entered the war reluctantly, two years after it began in Europe. It left the war as the indispensable nation — not by design but by the coincidence of geography, industrial capacity, and timing. The choices made in the years immediately after the war — about the United Nations, about NATO, about the Marshall Plan, about the structure of the postwar international order — would determine whether that dominance would be used to build a stable world or to pursue narrow national advantage. The architects of the postwar order, whatever their limitations, understood the weight of that choice.