Union. But demonstrations broke out in Belgrade against the decision, and on 27 March, the opposition overthrew the government in a coup d'état. The new Yugoslav government refused to ratify the signing of the Tripartite Pact, though it did not rule it out. Adolf Hitler reacted by launching the invasion of Yugoslavia on 6 April 1941, allied with forces of Italy and Hungary. On 10 April, German troops entered Zagreb and on the same day, the German-Italian puppet state, the Independent State of Croatia (, NDH), was installed. The Ustaše were put in power by Hitler who appointed Ante Pavelić as the leader (Poglavnik) of the NDH. Yugoslavia capitulated to the Axis powers on 17 April. The Ustaše, a fringe movement in pre-war Croatia, attempted to garner support among ordinary Croats and Bosnian Muslims, but never attracted significant support among the populace. The ceding of territory to Italy was a particular blow to their popularity. Special status was given to the German minority, whose members served in the NDH military forces (Einsatzstaffel), and were organized as an autonomous body. From 1942, German minority members were enlisted in the SS Prinz Eugen division. Following the occupation and division of Yugoslavia, German and other occupation forces introduced anti-semitic laws in accordance with the Nazi Final Solution plan. In the NDH, the Ustaše enacted their own Race Laws, and embarked on a campaign of genocide against Serbs, who were Orthodox Christian, as well as the Jewish and Roma populations throughout the country. It established a concentration camp system, the largest of which was Jasenovac, where 77,000–100,000 people were murdered, the majority women and children, primarily Serbs, Jews and Roma, but also anti-Fascist Croats and Bosniaks. Around 29–31,000 Jews, or 79% of their pre-war population in the NDH, were killed during the Holocaust, mostly by the Ustaše. Almost the entire Roma population of around 25,000 was annihilated. The number of Serbs killed by the Ustaše is difficult to determine. The United States Holocaust Memorial Museum estimates that the Ustaše killed between 320,000 and 340,000 Serbs Croatian demographer Vladimir Žerjavić calculated the population losses of Yugoslavia, and estimated the total number of Serb civilian and combatant deaths in the NDH at 322,000. Of the civilian casualties, he estimated that the Ustaše killed 78,000 Serb civilians, in direct terror and in concentration camps, and the rest died at the hands of the German and Italian forces,