The Israeli military’s mission to rescue four hostages was a rare operation that required weeks of planning, and was given the final go-ahead just a few minutes before it commenced on Saturday morning, according to Israeli officials.

Israeli special forces, backed by the military, intelligence and air force, raided two buildings several hundred feet apart in a neighborhood in Nuseirat, in central Gaza. They brought home the four hostages — Noa Argamani, 26; Almog Meir Jan, 22; Andrey Kozlov, 27; and Shlomi Ziv, 41 — alive and in good medical condition. One police officer, part of the force that led the raid, was killed.

Scores of Palestinians, including women and children, were killed during the rescue operation, according to local Gaza health officials. The Israeli military said it had targeted militants who had threatened its forces as they sought to extract the hostages. Neither the Israeli military nor Palestinian health officials provided a breakdown of civilians and combatants killed in the raid.

Israeli troops have swept through much of Gaza since their ground invasion began in late October. But they have managed to rescue only seven living hostages in three separate military operations, with roughly 120 captives remaining in Gaza. Several proposed rescue missions did not go forward for fear that the hostages or the forces would die in the process, according to two Israeli defense officials, who spoke on condition of anonymity to discuss the sensitive operation.

In December, Israeli special forces tried to rescue a hostage from Hamas captivity, according to the two defense officials. Sahar Baruch, an Israeli hostage, was killed during the exchange of fire and two Israeli officers were seriously wounded.