The Second World War was arguably the most significant period of the 20th century. It brought about major leaps in technology and laid the groundwork that permitted post-war social changes including the end of European colonialism, the civil rights movement in the United States, and the modern women’s rights movement, as well as the programs for exploring outer space. The primary combatants were the Axis nations (Nazi Germany, Facist Italy, Imperial Japan and their smaller allies) and the Allied nations, led by Britain (and its Commonwealth nations), the Union of Soviet Socialist Republics and the United States of America. The Allies were the victors. Two superpowers, the USA and USSR, emerged from World War II to begin a Cold War with each other that would define much of the rest of the century.