The Ustaše massacre nearly 200 Serbs in the village of Gudovac, the first massacre of their genocidal campaign against Serbs of the Independent State of Croatia.

The Ustaše was a Croatian fascist and ultranationalist organization active, as one organization, between 1929 and 1945. It was formally known as the Ustaša – Croatian Revolutionary Movement. From its inception and before the Second World War, the organization engaged in a series of terrorist activities against the Kingdom of Yugoslavia. It collaborated with IMRO to assassinate King Alexander I of Yugoslavia in 1934. During World War II in Yugoslavia, the Ustaše went on to perpetrate the Holocaust and genocide against its Jewish, Serb and Roma populations, killing hundreds of thousands of Serbs, Jews, Roma, as well as Muslim and Croat political dissidents. The ideology of the movement combined fascism, Islamism, Roman Catholicism and Croatian ultranationalism.