For weeks this fall, Avi Markson basked in the warmth and bonhomie of his family back in Israel — a perfect first vacation, he said, from the new San Jose-based home remodeling job that he scored earlier this year.

Then came the air raid sirens, the decision to cancel his flight back to the Bay Area, and the message to his San Jose employer that he wouldn’t be returning to work anytime soon.

“There was no thought about it,” Markson said. “If my brothers are fighting, I’m going to be fighting.”

Across the Bay Area, numerous Israelis put their lives in California on hold this week to either stay put in their homeland or jet halfway across the world to aid in Israel’s response to the deadliest attack on its soil in decades. Some were active reservists in the nation’s armed forces who ranked among the 360,000 Israelis called to action as part of the country’s largest military mobilization in decades. Others, such as Markson, opted to either volunteer in the nation’s armed forces or join in civilian relief efforts across the country.

In doing so, they left children, careers and comfortable lives here in the Bay Area for a war with few parallels in Israel’s history.

“I did have a life there, but none of that matters now, if I’m being honest,” said Markson, 25, who was born in Israel and came to the U.S. after his mandatory three-year stint in Israel’s military as a young adult. He moved to San Jose two years ago and recently began work as a project manager with O.T Bay Builders.

“The only thing that really matters now is to fight this war and make them (Hamas) pay for what they did — and bring back the peace, and mainly the quiet, to all the citizens here in Israel,” he added.

Multiple other Bay Area residents found themselves torn between returning from vacation and giving aid to their homeland this week.

A decades-long Bay Area resident, Yoav Ben-Shushan landed in Israel on Oct. 5 with his family for their annual trip to Israel, visiting relatives and reveling in the picture-perfect weather along the northern coastal town of Atlit. But a day after Hamas’ attack, he arranged for his wife and two kids, ages 7 and 5, to fly back to Mill Valley while he signed up to volunteer with humanitarian efforts near Tel Aviv.

“I don’t think I’d ever be able to forgive myself if I got on that airplane with my kids and wife,” Ben-Shushan, an executive director of Israel Bonds. “Knowing that people need help here, there are human instincts that we all follow.”

Ben-Shushan spoke Friday evening via WhatsApp after having aided with a command center for humanitarian relief — distributing blankets, mattresses, beds and clothes for Israelis in need. He was “exhausted,” having put in 18-hour days this week aiding a group that has shifted from protesting the government’s judicial reforms to aiding displaced civilians, as well as soldiers in the fight against Hamas.

“Once you grow up in Israel, it’s ingrained in you for the love for the country, the people, the culture,” he said. “I’m not religious, but home is home.”

It remains unclear exactly how many Israelis living in the Bay Area and California either left this week to return to Israel or extended trips in the country to serve. Securing a flight overseas has been difficult for many, given how many commercial airlines have cancelled flights to Tel Aviv. And many Jewish people were already vacationing in Israel for the joyous Sukkot holiday, which ended the day before the attacks.

Still, the ethos of military service runs deep in Israel, with laws mandating at least three years of military service for men and two years for women. It all hearkens to an abiding desire among Israelis to defend the nation against the terrors that Jewish people have faced throughout history — making it “really a central institution to Israeli life and for many, many, many years the most respected institution in Israeli life,” he said.

Even active reserve duty — during which Israelis spend a few weeks a year serving the military while always on call in case of war — has been viewed as an essential part of life for the country, given the hostilities that Israel has faced from surrounding counties.

“The neighborhood is not such that you can just ignore it,” Ido Segev, a former lieutenant colonel in the Israeli armed forces who now lives in the Bay Area and has helped Israelis return to the Middle East following Hamas’ attacks. “We know if we don’t have a strong army defending the country, we won’t have a country. People understand it’s a must, it’s a requirement.”

That legacy of service has been tested in recent years, said David Myers, a professor of Jewish History at UCLA, including during a recent spate of protests against the Israeli government and Israel Prime Minister Benjamin Netanyahu’s controversial attempt to cut the power of Israel’s judiciary. Most of the thousands of Israelis living in the Bay Area, and most of the region’s Jews, opposed that move which led to massive protests, said Oded Hermoni, co-founder and managing partner of Silicon Valley venture capital firm J-Ventures.

But the brutality of Hamas’ attacks on Israelis have pushed Hermoni and many other Israel-connected Bay Area friends and associates to suspend their politics, he said.