They were not alive at the time of the Yom Kippur War, a half-century ago, another debacle at a moment of Israeli inattention, even if the war was ultimately won. The most ready comparison they make is to Sept. 11, 2001, a shattering moment when the United States experienced the slaughter of civilians, the evaporation of any sense of security, and a devouring, disorienting shock.

Mr. Morag’s initial reaction was: “Just eliminate them, eradicate them all, Hamas has to be destroyed. Israelis cannot stay in a place where the Palestinians next door are led by a group using the money they get to spread terror.”

But this has given way after a week to a more nuanced reflection.

“I am aware that in Gaza people are living a life with no hope,” he said. “To do such things, you have to get to a place where you don’t value your life anymore, where you are ready to die. These are monstrous acts that come from hatred and despair and brainwashing, but I would like to separate Hamas, an inhuman organization, from the Palestinian people.”

That, given the pitch of retaliatory fury in Israel, and a bombardment of Gaza that has already killed more than 1,900 people, according to the Palestinian Health Ministry, is likely to be very difficult. Secretary of State Antony J. Blinken has urged Israel “to take every possible precaution to avoid harming civilians,” but has also made clear that Israel has the United States’ full and unequivocal support.

This American backing has meant a lot to Bar Matzner, who, along with her husband, Lior Matzner, had left their two young children with their parents to attend the festival. “We just needed to get away from the stress of work, the stress around security, to experience a moment of freedom,” she said.