Following the Invasion of Yugoslavia in April 1941, the Axis powers occupied the entire territory of the Kingdom of Yugoslavia and established a puppet state, the so-called Independent State of Croatia (NDH) on the territory of present-day Bosnia and Herzegovina and Croatia. The Ustaše government saw Serbs, Jews, Romanis and antifascist Croats as a disruptive element and enemies of the Croatian people, and immediately started with their prosecution. Upon the establishment of the NDH, Ustaše officials immediately began making harsh statements against the Serbs. Although some of the prominent Serbs first offered cooperation to the new Ustaše government, Serbs were outlawed. During the first months of NDH's existence, numerous legal decisions were made against the Serbs: they had to leave the public service, had to move to the northern parts of Zagreb, could walk through Zagreb only during the day, had to wear a badge with the letter "P" (stood for "Pravoslavni", meaning Orthodox Christians), the name of their faith was changed from Serbian Orthodox to Greek-Eastern, and usage of the Cyrillic script was prohibited. Ustaše were making lists of Serbs which they used for deportations to Serbia. About 175,000 Serbs were deported from NDH to Serbia during the first two years of NDH's existence. Many historians and authors describe the Ustaše regime's mass killings of Serbs as meeting the definition of genocide, including the present-day Croatian and Bosnian high officials, Yad Vashem the Holocaust memorial center and Raphael Lemkin who is known for coining the word "genocide" and initiating the Genocide Convention. Sisak and Jastrebarsko concentration camp were specially formed for children. Diana Budisavljević, a humanitarian of Austrian descent, carried out rescue operations and saved more than 15,000 children from Ustashe camps.