The news that three Israeli hostages were mistakenly shot and killed last month in Gaza by soldiers meant to save them outraged many in Israel, who have since demanded answers about how the army conducts itself on the battlefield and safeguards civilians.

The three male hostages, captured by Hamas terrorists near the Gaza border on Oct. 7, were killed in Gaza City on Dec. 15. The men, aged 24, 26, and 28, were unarmed when they were shot. They had removed their shirts to reveal that their bodies were not strapped with explosives, and they were waving a makeshift white flag.

A military investigation is underway, but immediately after the shootings, officials said the army’s rules of engagement had been violated.

“The shooting of the hostages was carried out contrary to the open-fire regulations,” said Lt. Gen. Herzl Halevi, the Israeli military’s chief of staff. “Shooting at someone who raises a white flag and is seeking to surrender is absolutely prohibited.”

The killings shocked Israelis, for whom the military is a revered national institution in which service for most adult citizens is compulsory. Israelis are taught as early as grade school about the “purity of arms” doctrine preached by the Israel Defense Forces — the idea that soldiers must never use their weapons or power to harm noncombatants. Every Israeli soldier carries in his or her pocket a printed copy of “Spirit of the I.D.F.,” guidelines that lay out the military’s values, said Nir Dinar, an army spokesman.

While the deaths of the hostages brought questions about the military’s rules of engagement home to Israelis, human rights groups and the United Nations have said the military’s failures to properly enforce those rules most often apply to troops’ frequent interactions with Palestinians.

The details of the rules of engagement — the conditions under which soldiers are permitted to open fire — are classified because publicizing them would enable enemy forces to take advantage of them, said Mr. Dinar, adding that they were consistent with international law.

Maj. Gen. Yehuda Fuchs, the head of the military’s Central Command, specified in a letter to soldiers last year that in order to open fire, troops must believe there is a “clear and immediate danger.” Under the rules, he wrote, soldiers should discharge their weapons only in a “life-threatening situation.”

The U.N. body that monitors the human rights of Palestinians called on Israel on Dec. 20 to investigate accusations that soldiers had “summarily killed” at least 11 unarmed Palestinian men in Gaza City a day earlier. The Israeli military categorically denied the accusation. Soldiers, the military said, had encountered armed militants in the building, clashed with them and killed some. For some members of the Israeli public, the hostage deaths were the latest eye-opening incident to highlight the gap between the army’s rules and the reality of war.

In November, an off-duty soldier killed an Israeli lawyer who had chased two Palestinian gunmen that had fired into a crowd of people waiting for a bus in Jerusalem. The soldier said he mistook the lawyer, Yuval Castleman, 37, for one of the assailants. But in a video of the incident, Mr. Castleman is seen dropping to his knees, throwing down his weapon, raising his hands in the air, saying he was Israeli and pleading with the soldier, “Don’t shoot.”

Three people at the bus stop were killed in the attack before Mr. Castleman intervened, and five were injured. The soldier was placed briefly under house arrest after a public uproar, and then his passport and right to carry a weapon were taken away.

And on Wednesday, the Israeli military said that Sahar Baruch, 25, who was taken hostage on Oct. 7, was killed last month during a rescue attempt. The military said it was not yet possible to determine whether he was killed by Hamas or by fire from its own forces.

Well before the war in Gaza, human rights groups had for years accused the army of failing to enforce its rules of engagement in the occupied West Bank and not punishing those who violated them.

According to a 2022 report by the Israeli human rights group Yesh Din, which was based on data provided by the army for the years 2017 to 2021, about 20 percent of 1,260 complaints by Palestinians about alleged offenses committed by Israeli soldiers against them or their property were investigated, and less than 1 percent resulted in a criminal indictment.