Mihailović undertook a military and political structuring of the movement. In August 1941, he formed the Chetnik National Committee as an advisory body. It included former politicians and members of organizations such as the Serbian Cultural Club, with a Greater Serbian ideological orientation. Outside Serbia, various independent groups were formed that shared the same ideology as the Chetniks. These groups took part in armed uprisings against the Ustashe-led Independent State of Croatia (NDH), an axis puppet state established in occupied Yugoslavia, in the summer of 1941. The uprisings were a reaction to the genocidal policy implemented by the Ustashas against Serbs. Mihailović sought to assume command of the insurgents and integrate them in the Chetnik movement. In the first months of the war, the Chetniks cooperated in their anti-Axis activities with the communist-led Yugoslav Partisans under Josip Broz Tito, with whom they later came into conflict.