TEL HASHOMER, ISRAEL - Since Israel's founding, the military here has served not just as a defender against outside threats, but as the glue that brings together a patchwork nation of immigrants.

Now, the Israel Defense Forces' position as the country's most venerated institution appears to be slipping. While service is compulsory for most young men and women, a growing minority is avoiding conscription, leaving planners to worry the military won't have the troops it says it needs.

The characteristics of those who do serve are changing in striking ways. Officers who are ideologically opposed to relinquishing Israeli control of the West Bank are taking on a more prominent role, potentially complicating any eventual Israeli withdrawal of Jewish settlers from the territory as part of a peace deal with the Palestinians.

A recent series of scandals has reignited debate about morals and accountability in the armed forces, and analysts say public trust in the military is declining. Last month, a YouTube video of a dancing Israeli soldier shimmying near a bound and blindfolded Palestinian woman went viral on the Internet, further embarrassing the military.

"The military understands its position has eroded," said Yagil Levy, a professor at Israel's Open University and a leading expert on the military.

The share of military-age Jewish Israelis who don't serve grew from 12.1 percent in 1980 to 26 percent in 2007, according to a study by Haifa University political scientists published in August. The military projects that figure will reach 43 percent by 2020. And the portion of 11th- and 12th-grade males who said they would volunteer if service was not mandatory was only 58 percent in 2007, compared with 94 percent in 1988, the study found.

"Fifteen or 20 years ago, not serving in the army or not doing miluim [reserve duty] was something to be ashamed of and today, I wouldn't say it's the other way around, but definitely people have no problem to declare that they just don't go to the army or don't serve in the reserve duty," said reservist Shahaf Kieselstein, who handles combat unit recruitment. Youth icons who have evaded service in recent years like Leonardo DiCaprio's girlfriend, model Bar Refaeli, give legitimacy to evading service, he said. "It trickles down."

A changing population
The biggest explanation for the declining service rate is the growing number of ultra-Orthodox Jews, who study full-time in yeshivas, or religious schools, and are eligible for exemptions from military service. Others are exempted for health reasons, criminal records or because they live abroad.

Today, the military loses 13 percent of its potential draftees because of ultra-Orthodox exemptions, compared with 4 percent 10 years ago. In 2020, that number is expected to reach 20 percent because of a drastically higher birthrate among the ultra-Orthodox compared with secular Israelis. To help persuade more ultra-Orthodox to volunteer, the Israeli military is expanding its efforts to provide special food, extra time for prayer and other adjustments to make service compatible with their religious practices.

In the past, officers largely came from secular, elite families from the Tel Aviv area or the collective farms known as kibbutzim. But today, increasing numbers are observant Jews who tend to be more politically oriented, more committed to the Zionist cause and more integrated into society than the ultra-Orthodox. An Israeli military magazine, Ma'arachot, reported recently that one-third of those who complete officers' courses come from this group, a roughly tenfold increase over a decade ago.

Kieselstein, a reserve officer from an infantry combat unit who lives in Har Adar, a community midway between Jerusalem and Tel Aviv, has been doing reserve duty for 18 years. He's watched the changes among the officers.

"What I do feel is a bad thing is the miluim are not spread equally among the potential society parts that could take on the burden," Kieselstein said. "The reality is I'm almost 40 now. The only reason I keep serving is because I want to. People who don't want to serve, they find a way to get out early. The army hardly tries to fight back. That's a paradox I cannot explain. On the one hand they talk about shortages. But all my friends . . . if they don't want to serve after 30 or 35, they get out of it and the army does nothing about it.''

While the military says it still fills its combat unit quotas today, officials say they don't have enough soldiers for support units and administrative jobs.

"Right now we have a problem because we lack soldiers," said Brig. Gen. Amir Rogovski, head of personnel planning in the IDF's manpower branch. "When you see the forecast for 2020, it's going to be worse.''

But one 22-year-old soldier, identified only as D, says the motivation to serve in combat is still strong. "People want to be fighters because that's what society values," said D, who lives in the Jewish settlement of Ma'aleh Adumim outside Jerusalem and will complete his three-year service on Sunday.

He said he most valued the personal enrichment. "I was drafted as a child with a head of a kid, and now I feel different, if it's the music I listen to, if it's in my behavior, even if in the clothing that I wear," said D, who served in the elite Golani infantry brigade.

The IDF does not make public the size of its force. But according to Tel Aviv University's Institute for National Security Studies, an independent research institution, Israel maintains a standing army of 176,500 soldiers and another 445,000 reservists. The Jerusalem Post reported in May that the military faced a shortage of 10,000 soldiers. Israel has a total population of about 7.6 million, of which about 5.7 million are Jewish Israelis and 1.5 million are Arab Israelis, according to Israel's Central Bureau of Statistics. Arab Israelis are not drafted, and very few volunteer.

Public relations push
With peaceful relations between Israel and former foes such as Egypt and Jordan, some Israelis have questioned the need for maintaining so many combat troops.

In recent years, Israelis successfully pushed to shorten the length of reserve duty. But periodic efforts to make service in the IDF voluntary have gone nowhere. Military officials say that, given today's low motivation levels, they would be unable to recruit enough volunteers to meet their needs.

"You ask me, 'Why do you have to convince or promote the service when you have a compulsory service?'â??" Rogovski said during an interview at the IDF induction center in Tel Hashomer. "If we don't explain every day the importance of serving the country and the importance of being in the military service, we won't fill the numbers and the quality needs for the next decade."

Most Jewish men in the country are required to serve three years and most Jewish women two, and the military historically had little direct contact with future soldiers before their induction.

But, faced with projected shortages, the IDF is making an unprecedented investment in public relations. Next year it will introduce several "Mobile Draft Offices," to be dispatched to some 700 schools a year to generate enthusiasm for military service among Israeli teenagers. The IDF is also belatedly embracing SMS, or text messaging, as well as online chats and other technological means employed for years by militaries around the world to interact with youth before they are drafted.

Casualties less accepted
The IDF remains by far the most trusted public institution in Israel - although a survey last year by the Israel Democracy Institute, an independent research center in Jerusalem, found a small five-year decline in the country's faith in the military, from 86 percent in 2004 to 79 percent in 2009. And the draft is still a core rite of passage in mainstream Israeli society, with acceptance into an elite unit generating the kind of pride an American family feels when a child gets in to Harvard.

But these days, according to Dan Sagir, a former military correspondent for the newspaper Haaretz, some wealthy Tel Aviv families are hiring Arabic tutors to boost their children's chances of being drafted into intelligence units rather than risk ending up with dangerous combat assignments.

"I think it's like in every place around the world," said the IDF's Rogovski. "In the big cities, Tel Aviv, you have less soldiers that volunteer for combat units. And from the . . . geographical periphery, you have more youth that want to serve in combat units."

In Israel's early years, when the country was fighting for its survival, the public had a higher tolerance for military casualties. As the country has grown more powerful, that has changed.

Officers point to the war between Israel and the Lebanese Shiite militia Hezbollah in 2006. The Israeli campaign was waged mostly from the air, they say, because politicians and military planners understood the public's tolerance for Israeli casualties had dwindled. The fighting left Hezbollah intact and reminded Israelis of the persistent need for ground troops.

For Israel's military, there is enough uncertainty to require the maintenance of a large force: conflicts with Palestinians, Lebanon and Syria remain unresolved, and the prospect of a confrontation with Iran looms as the Iranian nuclear program advances.

But in a recent opinion piece in Haaretz, Sagir, an avowed leftist whose son will soon be drafted, worried that the Israeli government's failure to reach a peace agreement with the Palestinians would further erode public enthusiasm for military service.

"Israeli society is at a crossroads with respect to conscription in the IDF," Sagir wrote. "The issue is the erosion of the legitimacy of service in the IDF as the conflict drags on."