“Hamas’s insistence on holding onto hostages as leverage, and Netanyahu’s politically driven refusal to proceed with phase two of the cease-fire, which called for an end to the war and the release of all living hostages, led to this escalation,” said Daniel B. Shapiro, a former U.S. ambassador to Israel.

D EIR AL-BALAH, Gaza Strip — Israel launched a wave of airstrikes across the Gaza Strip early Tuesday, saying it was striking dozens of Hamas targets in its heaviest assault in the territory since a cease-fire took effect in January. Palestinian officials reported at least 44 deaths.

Israeli warplanes pounded Gaza on Tuesday, killing hundreds of Palestinians in what is the first major attack since Israel and Hamas entered a fragile U.S.-backed cease-fire in January.