The Ustasha policy towards Serbs further drove a number of them joined either Chetniks or the Yugoslav Partisans who were particularly strong in the regions of Lika, Kordun and Banovina. In 1941–42, the majority of Partisans in Croatia were Serbs, but by October 1943 the majority were Croats. This change was partly due to the decision of a key Croatian Peasant Party member, Božidar Magovac, to join the Partisans in June 1943, and partly due to the surrender of Italy in September 1943. Ustahe ceding Northern Dalmatia to fascist Italy, Italian terror of the population and misrule of the Ustahe and Axis invaders would further push Croats towards the partisans. At the moment of the capitulation of Italy to the Allies the Serbs and Croats were participating equally according to their respective population sizes as it was in Yugoslavia as a whole. Eventually, Serbian percentage dropped in favor of Croats by the end of the war amounting to 28.6% in 1944 in Croatia. The Serb contribution to Croatian Partisans represented more than their proportion of the local population. After the invasion of Yugoslavia by Axis forces, Serbian uprisings broke out under the Chetnik leadership in Gračac, Srb, Donji Lapac, Drvar and Bosansko Grahovo. The policy of the Chetniks under the leadership of Draža Mihailović varied from the struggle with the Nazis to tactical or selective collaboration with them in different periods throughout the war. The goal of the Chetniks, based on a 1941 directive, was the creation of an ethnically homogeneous Greater Serbia. The largest Chetnik massacres took place in eastern Bosnia within the NDH where they preceded any significant Ustashe operations. In the territories they controlled, Chetniks engaged in the ethnic cleansing of the Croat and Muslim civilian populations. However, they also collaborated with some of the Ustashe forces in northern Bosnia and they fought together against the Yugoslav Partisans during the Case White.