After the German invasion of the Kingdom of Yugoslavia on 6 April 1941, the Ustaše formed their government with Ante Pavelić as leader. Four days later Kvaternik proclaimed the establishment of the Independent State of Croatia (NDH) and formed the first Ustasha government. At the same time, at Kvaternik's request, Vladko Maček (the leader of the Croatian Peasant Party, who had refused to cooperate with the Germans when they requested he lead the new nation) told the people to cooperate with the new regime.