Three days into Josh Warhit’s first-ever visit to Israel, as a 16-year-old on a summer tour, war broke out in Lebanon, which transformed the group’s itinerary — and his life plan. On Tuesday, with talk rampant about the possibility of an imminent Israeli attack on Iran, Mr. Warhit became a citizen of Israel to enlist in its army.

“Our parents were freaking out,” Mr. Warhit, now 22, recalled of that first trip during the war against Hezbollah. “It only made us more thirsty. I love the Jewish people. Love involves commitment. Right now we need people to commit.

“Of course it’s scary,” he added, regarding Iran, “but if you feel a commitment, that’s the thing to do.”

Mr. Warhit, who grew up in New Rochelle, N.Y., and graduated from the University of Rochester after spending several summers in Israel, was one of 127 soldiers-to-be who landed Tuesday morning at Ben-Gurion International Airport here. They arrived after a week of intense media speculation that an Israeli strike on Iran’s nuclear facilities was increasingly likely, though the premier enemy of the moment was not mentioned by name during a hero’s welcome that included a live band, balloon hats and a speech by Prime Minister Benjamin Netanyahu.

Part of a growing cadre of what are known as lone soldiers, they left behind parents, girlfriends, cars and stuffed animals to become infantrymen, intelligence officers, paratroopers and pilots in a formerly foreign land. All told, according to a military spokeswoman, Israel has enlisted 8,217 men and women from other countries since 2009, 1,661 of them from the United States, second only to Russia’s 1,685.

They receive a host of special benefits: three times the typical soldier’s salary, a personal day off each month, a free flight home and vouchers for holiday meals. But with few exceptions for dual citizens from certain countries, they serve side by side in even elite combat units with native Israelis drafted out of high school.

“Their motivation is often way higher than the average Israeli,” said Col. Shuli Ayal, who oversees the lone-soldier program. “They want to make their service as meaningful as possible.”

Mr. Warhit, for one, aspires to the Givati Brigade, a ground-forces unit formed before Israel became a state in 1948 that in the past decade has been active around the Gaza Strip. Elona Brage, 22, the daughter of doctors from San Francisco, hopes to be a medic — “anything but combat,” she said. And Daniel Rechenbach of Ridgewood, N.J., a graduate of Clark University whose sisters moved to Israel ahead of him, wants to join Oketz, the canine unit.

“I hope to spend my time in Israel protecting those I love, not torturing those who hate me,” Mr. Rechenbach, also 22, said in an e-mail interview ahead of the flight. “If my dog and I successfully locate materials meant to harm Israeli soldiers or civilians, I would be incredibly proud.”

As they adopt new identities as Israeli soldiers, the recruits are joining a military, and a society, struggling with its own identity crisis. The Supreme Court in February declared illegal a program exempting thousands of ultra-Orthodox yeshiva students from the draft, and Parliament failed to come up with a new program to enroll them as well as Palestinian citizens of Israel into the army or civilian service. On Monday, ultra-Orthodox leaders issued a warning to young men not to sign draft notices.

Mr. Netanyahu welcomed the troops on Tuesday into a battle against what he called “a new anti-Semitism.”

“You’ve decided to defend the Jewish future,” he told them. “In previous times, for almost two millennia, the Jews could not defend themselves.”

According to the Ministry of Immigrant Absorption, the number of people coming to Israel over all rose to 19,020 last year from 15,875 in 2008, after a steady slide from 61,723 in 2000 and the huge influx of nearly one million, mostly Soviet Jews, in the 1990s.

The soldiers were among 351 new immigrants arriving Tuesday on a flight chartered by Nefesh b’Nefesh, a 10-year-old group that has helped bring 30,000 people here. On board were five sets of twins; 16 people joining children and grandchildren who had preceded them (several of these families designed and wore special T-shirts chronicling the generational influx); Jamie Geller, a cookbook author and founder of the kosher Media Network; and six dogs. The oldest newcomer was 85, the youngest was born in July.

Hundreds arrived at the airport to greet them, bearing homemade signs cheering Ilan and Matz, Sandy and Jerry, Mani and Abby. “The Frieds are home at last!” read one. “Bruchim haba’im, Bubbe and Zayde,” said another, combining the Hebrew for ‘welcome’ with the Yiddish for grandma and grandpa.

The center of the celebration was the soldiers, who wore army-green T-shirts and broad smiles. Most came through Garin Tzabar, a diaspora offshoot of the Israel Scouts program, and prepared over four weekend workshops since January. They hugged and held one another in a manner reminiscent of summer camp or college orientation. Before basic training this fall, they will study Hebrew on kibbutzim around the country.

There were young women with pierced lips (the studs will come out upon enlistment) and men with skullcaps and prayer fringes who danced in a circle among themselves. Many are the children of Israelis, for whom army service is a staple of life, but Mr. Warhit, whose four grandparents were all born in America, had some convincing to do.

“You want to teach your kids to love Israel, but you don’t want them necessarily to take you so literally,” his mother, Ilissa Warhit, said in a telephone interview after what she described as 24 hours of nonstop tears. “You always know the dangers, and it’s very far away.”

Last week, Mr. Warhit and his father spent four days playing in a wood-bat baseball tournament in Cooperstown, N.Y. Though the soldiers-to-be are allowed three suitcases of 70 pounds each, he filled two, at 40 pounds each, and a small duffel. The hardest thing, he said, has been explaining his choice to non-Jewish friends.

“Sometimes life in the States is just so easy, you think, ‘Maybe I should go to law school,’ ” he said. “I love my family, I love my friends and I love the Jewish people. The Jewish people don’t need another Jew in suburban New York.”