The first part of the chapter discusses Serbia during the Great War. Following initial military successes, Serbias army was forced to retreat, together with the government and the royal family, to the Greek island of Corfu in late 1915. By late 1918, a recuperated Serbian army, together with its allies, liberated Serbia and occupied much of what would soon become Yugoslavia. Serbia suffered enormously in the war, but its domination of interwar Yugoslavia alienated non-Serbs and many formerly Habsburg Serbs. In response to the political crisis, King Aleksandar Karadjordjević introduced dictatorship in 1929. His project to create a unified Yugoslav nation had largely failed even before his assassination in 1934. The late 1930s saw a partial return to democracy, in contrast to developments elsewhere in East-Central Europe, a Serb-Croat compromise, and a move closer to Berlin and Rome. Serb officers and most political leaders rejected a pact with the Axis in 1941, leading to the invasion and partition of Yugoslavia by the Axis. The final part discusses resistance, civil war and collaboration and the German policy of reprisals against Serbs, Jews and Roma in occupied Serbia.