From the introduction: In 1939, German authorities began to concentrate Poland's population of over three million Jews into a number of extremely crowded ghettos located in large Polish cities. The largest of these, the Warsaw Ghetto, concentrated approximately 300,000–400,000 people into a densely packed, 3.3 km2 central area of Warsaw. Approximately 250,000–300,000 ghetto residents met their deaths at Treblinka during the two-month-long operation in 1942, another thousands in Warsaw Ghetto Uprising in 1943.