Thang Dang long felt close to the military, having grown up admiring an uncle who served in the U.S. Army during the Vietnam War. Now the 17-year-old is a soldier himself, a member of the Hawai'i Army National Guard since June.

"I always wanted to join the service; I just wasn't sure which one," said the high school senior. "It's a step for me to become a man."

The Hawai'i Guard attracted 388 newly enlisted soldiers during the year ending last September. That's better than the annual average of 300 to 350. Nationally, just over 69,000 people joined the Army Guard last fiscal year, up 40 percent from 49,000 in 2004.

The question is, will it last?

With the military rotating citizen soldiers through Iraq and Afghanistan every few years, experts are concerned the enthusiasm for the Guard may wane and fewer people will want to join and remain members.

"We shouldn't say, 'OK, the recruiting and retention numbers look OK, let's relax,' " said Christine Wormuth, a senior fellow at the Center for Strategic and International Studies, a Washington think tank.

"It's a fairly brittle situation."

The Pentagon this month informed 13,000 Guard troops in Arkansas, Indiana, Ohio and Oklahoma they should get ready to deploy again by early next year. Many of these troops returned from their last mission just two years ago.

It is not clear whether the military will need to continue mobilizing Guard soldiers this often.

In January, the Pentagon said it would give Guard members five years at home between involuntary deployments. But the latest call-up indicates it is having trouble meeting that goal.

This worries some Guard members, many of whom are part-time and have civilian jobs when not deployed.

Deployments can be hard on families left behind, as spouses are left to cope with abruptly becoming a single parent.

Some employers, particularly small businesses, struggle with lost sales and higher expenses when their workers are called up.

It's even tougher for self-employed Guard members who must figure out how to keep their businesses running in their absence.

Wormuth said she believes Guard members will accept being deployed once every six years, the frequency the Pentagon is targeting.

But she said there's a real possibility that recruitment and retention will suffer in Hawai'i and other states if the military continues to deploy Guard soldiers once every third or fourth year.

"We're asking these people to serve and serve and serve, but we're not building the systems that make it easy for them to do so," Wormuth said.

Like the recruitment data, retention figures are also currently strong.

Army Guard units across the country lost 56,000 soldiers last fiscal year, some 5,000 fewer than in 2004.

In Hawai'i, 528 soldiers left the Army Guard during the year ended in September. That's more than the annual average of 300, but it includes those who couldn't leave the prior two years because the 29th Brigade Combat Team deployed to Iraq.

Even so, a March study by the Commission on the National Guard and Reserves echoed Wormuth's concern, citing concerns about the stress deployments impose on families and employers.

"The long-term viability for both recruiting and retention remain highly problematic," the study said.

The commission, whose members are appointed by the defense secretary and the House and Senate Armed Services committees, said the Guard and Reserves were being used as an operational force even though they were organized as a reserve forces for the Cold War.

The commission plans to issue a final report in January that will include recommendations for how the Guard should adapt to changing times.

Maj. Gen. Robert G.F. Lee, the Hawai'i Guard commander, said his soldiers aren't likely to be among units mobilized soon because most just returned from Iraq a little over a year ago.

"Hawai'i is way down the list" of units to be mobilized, Lee said in an interview.

He added that the Pentagon's January decision to hire and train 92,000 additional active-duty Marines and soldiers should reduce the need for the military to call on the Guard so frequently.

He also likes how the Pentagon has decided to mobilize Guard members for no more than one year each deployment instead of 18 months.

Lee praised these moves as a good steps toward preparing the military for a "long war" against terror he said would take 50 to 75 years.

Even so, Lee said younger Hawai'i Guard members are adopting a wait-and-see outlook before deciding to stay in for the rest of their careers.

"For them it's 'I want to see what the next two, three or four years is like as opposed to the next 10,' " Lee said. "Because of the situation in Iraq and Afghanistan, I don't think anyone can look that far out."