How did the Holocaust begin and end?
The general concensus for the timeline of the holocaust is that it began following conferences by top German officials in 1942 and ended upon the camps liberation in 1945 by Allies troops.
Gradually the German persecution of Jews built up momentum so that by the time of the Wanasee Conference in spring 1942, the state sanctioning of murder was approved.
The Germans, along with their ardent supporters in Latvia, Lithuania, Ukraine and other countries continued their anti-Jewish work right up until the camps were liberated in Spring 1945. However the holocaust really did not end there. Just because the Germans were defeated in battle did not end the European wide hatred of Jews. In Poland in 1946 there were many tens of thousands of Jews murdered by the Polish Catholics for no other reason than ethnic hatred (possibly the casualties would have been even higher but by then the 'WWII holocaust' had thinned the Jewish ranks severely).
So great was the suffering of the Jews as an ethnic group that pro-Jewish forces in Britain and America began clammoring for a Jewish nation state. With Jews already illegally emigrating to Palestine, this became the natural location for the new nation. Founded 1947, Israel has been in an almost constant state of war with it neighbors, almost all of whom consider the Jews invaders and occupiers. Despite all the efforts of various heads of state this situation will not be resolved soon as the emotions run to too deep on both sides. It will be a millennium or more before this situation is resolved.
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However ...
1. The Holocaust had already begun by the time of the Wannsee Conference. Most historians now date the start of the genocide in 1941.
2. " In Poland in 1946 there were many tens of thousands of Jews murdered by the Polish Catholics for no other reason than ethnic hatred". Well, the highest figure I've seen anywhere is about 600, which is bad enough. A figure of about 330 is more common. As for the reason ... hardline Polish nationalists, like the Nazis, believed that the Jews were Communists. Of course, there may have been ethnic reasons too.