One brother chose to flee. His siblings chose to stay. None of them escaped the horrors of one of the deadliest Israeli campaigns in northern Gaza since the yearlong war began.

When Israel started its latest operation in early October to root out Hamas militants in the north of the Gaza Strip, the Nasr family were among some 400,000 people estimated by the United Nations to remain. They faced a near-impossible choice.

Staying put has meant enduring devastating bombardment. Hospitals are filled with the dead and wounded. Bodies have been left for weeks beneath the rubble. And it has meant hunger: Rights groups say Israel has imposed restrictions on aid so harsh they could amount to a starvation tactic.

But leaving has brought its own perils. Many civilians now believe that fleeing on the orders of Israeli forces is just as deadly.

When Ramy Nasr, 44, received an automated voice message from the Israeli army on Oct. 6 declaring most of northern Gaza an evacuation zone, including his hometown, Jabaliya, he took the warning to heart. His 17-year-old daughter, Mira, had already been severely injured by a strike in December, he told The New York Times.

A day after he received the message, Mr. Nasr followed one of the many orders Israel has issued in the past weeks — orders so numerous that its main ally, the United States, warned they risk violating international law.