 Complete the following phrase:  Between 1939 and 1941, in an attempt to resolve the Croat-Serb political and social antagonism in first Yugoslavia, the Kingdom established an autonomous Banovina of Croatia incorporating amongst other territories much of the former Military Frontier as well as parts of Bosnia and Herzegovina. In 1941, the Axis powers invaded Yugoslavia and in the aftermath the Independent State of Croatia which included the whole of todays Bosnia and Herzegovina and parts of Serbia Eastern Syrmia as well was declared. The Germans installed the Ustaše who had allegedly plotted the assassination of the Serbian King Alexander I of Yugoslavia in 1934 as rulers of the new country; the Ustaše authorities promptly pursued a genocidal policy of 