In 1941--two years into World War II and just before the Soviet invasion, Yugoslavia then ruled by Serbian King Petar II was invaded by the armed forces of Nazi Germany, and her axis allies Fascist Italy and Bulgaria.
Yugoslav communist Josip Broz Tito, born to a Croat father and Slovene mother, started a partizan resistence movement, embracing Serbs, Croats, Macedonians, Slovenians, Bosnians, Montenegrins, annd other ethnic groups.
However, because of its isolation, the part of Macedonia within Yugoslavia set up its own Partizan resistence movement which consisted of an uneasy alliance of Macedonian communists and nationalists. The Macedonian partizans as well as the civilian population endured a brutal occupation by the Bulgarians. Macedonia's Jewish population was wiped out by Bulgaria.
After the war, the Macedonian nationalists where largely arrested and forced to face stage-managed and rigged Stalinist show trials at the instigation of Tito and carried out by his Macedonian followers: Lazar Kolisevski, Lazar Mojsov, later to become President of the United Nations General Assembly and Yugoslavia's Foreign Minister, and Kole Chasule senior.
One of the most infamous communist show trials was of nationalist Metodija Andonov Cento, the first President of Macedonia within Federal Communist Yugoslavia. He was found guilty of trumped up charges in 1946. In 1990 a Macedonian court rehabilitated Chento.
Because large numbers of Macedonian nationalists had taken part in the Macedonian partizan resistence movement, they could not be accused of being fascist collaborators by Tito.
During the Greek Civil War, Tito had promised ethnic Macedonians autonomy within Greece if they sided with the Communists against the British and the American backed Greek monarchist forces. The result was a disaster as thousands of Macedonians, including children fled Greece for their lives. The United States under the command of General James Van Fleet had literally bombed parts of Greek controlled Macedonia back into the stone age.