Stalin's government promoted MarxismLeninism abroad through the Communist International and supported anti-fascist movements throughout Europe during the 1930s, particularly in the Spanish Civil War. In 1939 they signed a non-aggression pact with Nazi Germany, resulting in their joint invasion of Poland. Germany ended the pact by invading the Soviet Union in 1941. Despite initial setbacks, the Soviet Red Army halted the German incursion and captured Berlin in 1945, ending World War II in Europe. The Soviets annexed the Baltic states and helped establish pro-Soviet MarxistLeninist governments throughout Central and Eastern Europe. The Soviet Union and the United States emerged as the two world superpowers, and a period of tensions began between the Soviet-backed Eastern Bloc and U.S.-backed Western Bloc known as the Cold War. Stalin led his country through its post-war reconstruction, during which it developed a nuclear weapon in 1949. In these years, the country experienced another major famine and a period of antisemitism peaking in the 195253 Doctors' plot. Stalin died in 1953 and was succeeded by Nikita Khrushchev, who denounced his predecessor and initiated a de-Stalinisation process throughout Soviet society.