On 15 November 1940, German authorities in occupied Poland sealed off the main Jewish neighborhood in Warsaw in, which they sealed off from the rest of the city using a ten-foot-high wall topped by barbed wire. Warsaw, the capital of Poland, was a major center of Jewish life and culture before the start of World War II. The Jewish community was the largest in Europe, second only to New York City. The German occupation of Warsaw began in late September 1939, when Poland capitulated to the Germans and Soviets who had attacked it. By the end of 1940, nearly 400,000...