endeavor to ensure that the Serb population of Kosovo be – the area be cleansed of them and all Serbs who had been living there for centuries should be termed colonialists and sent to concentration camps in Albania. The Serb settlers should be killed." It is estimated that at least 10,000 Serbs were massacred and a further 200,000 expelled from Kosovo during WW2. In the Nuremberg trials, it was established that the SS Skanderbeg committed crimes against humanity in Kosovo against ethnic Serbs, Jews, and Roma. After the surrender of the Kingdom of Italy in September 1943, the German forces took over direct control of the region. In September 1944 the Soviet Union declared war on Bulgaria and occupied part of the country. A coup d'état on 9 September led to Bulgaria joining the Soviets. As result in the early October three Bulgarian armies, consisting of around 340,000-man, together with the Red Army entered occupied Yugoslavia and moved from Sofia to Niš, Skopje and Pristina to blocking the German forces withdrawing from Greece. The Bulgarians operated in conjunction with the Yugoslav and Albanian communist partisans. Kosovo was liberated by the end of November. It became a province of Serbia within the Democratic Federal Yugoslavia. The Kosovo Albanians, who had been promised self-determination if they joined the partisans, rebelled and martial law was declared. It took about six months for the area to be pacified after some 20,000 Albanians under Shaban Polluza resisted integration of Kosovo within Yugoslavia. Jewish deportations during the holocaust also occurred in the area. Socialist Yugoslavia (1945–1989) The province was first formed as a member of the Federal People's Republic of Yugoslavia under the leadership of the Partisan leader. This was to be the first time in history that the name of Kosovo came to espouse its current borders; prior to this, its borders, along with its status had fluctuated with time. These borders were drawn carefully so as to incorporate an area with a heavy concentration of Albanians. One such explanation for Kosovo's lines of demarcation never having been properly defined is that its Slavic and Albanian populations have even disputed the origins of the name. As such, the imaginary borders have also been disputed; for example, Albanians are of the belief that the Preševo Valley constitutes eastern Kosovo, whilst Serbs have rendered regions within today's Republic of Macedonia to be traditional Kosovo, such as Skopje,