Final answer:
The Nazis invaded the Warsaw Ghetto at dawn, specifically on the eve of Passover. The residents went into hiding and the organized resistance began.
Step-by-step explanation:
The Nazis invaded the Warsaw Ghetto early in the morning, specifically at dawn. They intended to liquidate the ghetto on April 19, 1943, which was the eve of Passover. However, when they entered the ghetto, they found empty streets as the residents had gone into hiding.