The young officer candidates, in uniforms and old American helmets, their M-16s slung over their shoulders, were blowing up balloons. Lilac, blue and red balloons. Then they attached them to targets.

The balloons were “hostages,” they said. The point was to hit the target but not a hostage. Of course, since some of these young men and women were training for office jobs, their skills were not always so acute. They did not kill any hostages, but sometimes they did not hit the target, either, their bullets piercing the desert hills.

Other candidates, combat soldiers, were considerably better shots. But the mix was intentional: virtually all Israel’s officers-to-be, from every military branch excluding pilots, pass through this institution in the desert hills of the Negev, near the natural wonder of Mitzpe Ramon, an enormous eroded crater.

Israel’s defense forces are considered among the world’s best, a people’s army that combines professionalism and informality, and serves as a melting pot for a complicated society with real enemies. Yet it also faces challenges, including an effort to recover from a poorly run war, a rise in the number of young people dodging military service and an increase in religious Israelis, many of them settlers, who serve.

The army has faced harsh criticism after the 2006 war against Hezbollah in Lebanon, and the Israeli defense minister, Ehud Barak, a former chief of staff who was Israel’s most decorated soldier, has complained that too many people are evading service.

“From the army of the people, the Israeli Defense Forces are gradually becoming the army of half the people,” Mr. Barak said. “A soldier must not feel that when he goes to battle that in the eyes of part of the society he’s a sucker.”

Col. Ziki Sela, who is in charge of personnel planning for the military, said it was important to distinguish between those who were not asked to serve — Israeli Arabs, ultra-Orthodox Jews, the ill — and the roughly 25 percent of eligible male draftees who found a way not to serve. That figure is nearly twice as high as in 1980, yet not much different from five years ago.

But some of the draft dodgers, both men and women, have been prominent in entertainment, including a famous model and five of the eight finalists in Israel’s version of “American Idol.”

Today, Colonel Sela said, about 54 percent of Israel’s 18-year-old men are being inducted, which is not enough to meet his needs, especially for support personnel. About 43 percent of eligible women do not serve either, he said, in part because a young woman can merely state that she “follows a traditional lifestyle” to be exempted as too religious for the army.

But of the 25 percent of eligible men who do not serve, many live overseas, have criminal records or medical exemptions. Colonel Sela said about 12 percent were draft dodgers. But some analysts, like Stuart Cohen, a professor of political science at Bar-Ilan University, argue that the real figure for true draft dodgers is 5 percent or less.

What the figures disguise, however, is the undiminished fervor of young men volunteering to fight in combat units, which make up roughly a third of the army. The Golani infantry brigade, for instance, gets 10 applicants for every place.

But in another challenge for the army, a large proportion of those volunteering for combat units — 30 percent to 40 percent — come from the “national religious” sector, Zionists who tend to wear knitted skullcaps and are frequently settlers. In the past, many fighters volunteered from Israel’s kibbutzim, or collective farms. But now, large numbers are “the new pioneers,” the children of settlers.

They are eager to fight Israel’s enemies. But as Israel contemplates new peace talks with the Palestinians — and an eventual withdrawal from large sectors of the occupied West Bank — the government and army worry that many of those soldiers, and officers, may refuse orders to dismantle settlements.

Col. Aharon Haliva, 40, is the commander of this school, which is almost as old as the state. A former brigade commander in the occupied West Bank, Colonel Haliva is blunt. “The army reflects the society, with all its strengths and problems,” he said. “After the second Lebanon war, people want to be able to believe in their army, which is themselves.”

He said he worried for a time that young people might refuse to become officers after the failures against Hezbollah in Lebanon. “It’s much easier to win battles when you understand why you’re there, and what you’re expected to do,” Colonel Haliva said in a tart comment on that war. “We all want to be part of a strong organization.”

By the time the candidates get here, “they know how to fight,” he said. “I’m not worried about how they use their weapons. I’m concerned with implanting the right values.”

But this school, like the society, is struggling with the great internal challenge of how, if ordered, to remove thousands of Israeli settlers from the West Bank — many more than the 9,000 torn with such national agony from Gaza.

The army draws many of its best combat soldiers and officers from the “national religious.” Here, they make up about 10 percent of the staff officers, 15 percent of the combat support officers and up to 40 percent of the combat officers, the colonel said. “You don’t find them in Tel Aviv, but all over the hills of Judea and Samaria,” he said, using the biblical names for the West Bank. “They are the pioneers of today.”

When there is a pullout from the West Bank, “a lot won’t serve in a disengagement, I’m sure of it,” Colonel Haliva said. “Just as some kids on the left don’t want to serve in the territories.”

He wants his officers “to have more questions than answers.” But it is his job and that of his staff to explain “the importance of what they’re doing, and the reasons they’re being ordered to do it,” he said. “After Gaza, we thought that maybe some of these kids would refuse to become officers, but it’s not true.”

Still, there are doubts. Levi Harvith, 22, is a member of the Golani infantry brigade, like the current army chief of staff. Tall, fit and articulate, he has already served in Lebanon and Gaza.

“We’re in elite units,” he said. “We’re trained in flexible thinking. We want to lead by example, but we’re encouraged to solve problems in more creative ways.”

Mr. Harvith sees himself as a leader. “In two months I’ll command 20 soldiers, and from them there will be maybe two officers, and that’s another 40 soldiers, and another 40 families. We have a big effect on the society.”

First commanders matter, he said. “The way I hold my weapon — it’s the way my first commander held it.”

He is also religious, he said. Would he have pulled people out of Gaza?

“That’s a good question,” he said, then paused. “For me, it’s not just a religious question but a moral question. I do what I’m told,” he said, pausing again. “Except in moral cases, that’s the point.”

Asked where he would seek advice, he said he would first talk to his father, and then to “previous commanders I admired.”

Would he talk to his rabbi? “Maybe my father would,” he said. “You need the right proportion of asking questions and obeying.”

The national religious are estimated to make up some 15 percent of Israel’s population, and they have growing influence in the officer corps. Yael Paz-Melamed, a leftist columnist for the daily newspaper Maariv, warned that the army was becoming “increasingly political and right wing.”

The “hesder yeshivas,” which combine military service and Torah study for some of the most religious candidates, also raise concerns. The hesder yeshivas now turn out 1,200 recruits a year, Colonel Sela said, a 40 percent increase in five years. “We’re not happy with that,” he said. “It’s too much. We want about 900.”

Israel rarely identifies future officers before they join the army. They are chosen by their commanders after a year or more in uniform, after a battery of tests and often after combat, to come to this place, known as Bahad 1, short for Instruction School No. 1.

About 6,500 cadets a year come through here, Colonel Haliva said, divided into those who will command offices, combat support units and combat units. “We have the young elite of the country here, full of motivation,” he said. “They want to become officers, it’s still a very strong brand in the society, and it’s a brand for life.”

Noa Leshem, 19, arrived here after 16 months in the military. An air traffic controller, she will command a platoon of them. “This place gives me tools,” she said. “What it means to be a leader, what it means to be a Jewish Zionist. I’m more clear-minded now about the army, about the relationship to democracy and the way we can improve.”

This semester takes only 15 weeks, with classes on technical subjects like navigation and weapons and courses on leadership, psychology, character and values.

There is a trip to Jerusalem to visit institutions like the Parliament, the Supreme Court and the Holocaust museum at Yad Vashem. It ends with a long combined armor exercise.

Then there are another 15 weeks of specialized training with their units. They graduate as first lieutenants and platoon commanders.

Shahar Heimann, 20, is a combat soldier, having served in Jenin, Nablus and Ramallah. He said the cadets were conscious of Israel’s social divide and how it could affect the army.

“Every soldier here sees himself as a company leader,” he said. “We can’t change the whole society, but in a smaller way, by leading our soldiers the best we can.”

He said it was important to mix with officer candidates from “all over the army and the society — the Druse, Bedouin, Ethiopians, Russians.”

“You see all the minorities,” he said, “and you understand their problems better.”