1940s: The world in flames

Because so many men left for military service, factories and offices faced severe labor shortages and recruited women to fill them, especially in wartime production. This pushed millions of women into jobs once closed to them and shifted long-held expectations about the kind of work women could do.

Wartime spending did it. Enormous government orders for weapons, ships, and supplies put idle factories and unemployed workers back into production almost overnight, ending the long slump of the 1930s and starting a boom that carried on well into the postwar years.

Victory left the United States and the Soviet Union as the only two superpowers, and their opposing political systems quickly turned wartime allies into rivals. Arguments over who would control postwar Europe hardened that distrust into a long standoff fought without direct battle.

The decade pushed forward radar, jet propulsion, mass-produced antibiotics, the first electronic computers, and nuclear power. Governments poured money into solving military problems quickly, and many of those wartime breakthroughs later changed medicine, travel, and daily life once peace returned.