Pfc. Casey Ow- ens is a Javelin gunner, preparing to carry the sophisticated antitank weapon into Iraq. He talks excitedly of a missile blasted from a tube on his shoulder soaring high in the air before smashing through the vulnerable top of an Iraqi tank.

The only problem is, he had never laid a hand on the weapon before Wednesday night -- and still has never fired one of the $80,000 rounds. Fresh from infantry school, where he specialized in shooting TOW missiles from the roof of a Humvee, Owens joined the Marines camped in the Kuwaiti desert less than two weeks ago and was asked to learn the new job to fill a shortfall in his battalion.

"I still feel pretty green," said Owens, 21, of Houston. "It's a lot to get used to, getting sent here so quickly. Most of these guys have known each other for a while. I have had to pack a lot into the past 10 days."

The Marines poised to invade Iraq figured they would be at war by now. But as they wait for word from Washington, members of one particularly fresh-faced unit are using the extra time to get comfortable with weapons and acclimate to military life. The 1st Battalion, 7th Infantry Regiment, which boasts a storied combat history, has welcomed 300 new Marines into its ranks of around 900 in the past few months, including 19 who, like Owens, finished their infantry training while the rest were already here in Kuwait.

The battalion, slated to be one of the first to cross the border, is one of the youngest in the Marine Corps, with an average age of 20.

While some complain that sitting through sandstorms and increasingly hot weather is bad for morale, their commanders appreciate the extra time they are getting to prepare the troops.

"I know people make the case that all the waiting around dulls your senses, but for us the extra few weeks has been great," said Capt. Tom Lacroix, commanding officer of the 1st Battalion's Charlie Company. About 150 of the 180 Marines under his charge have joined the company since August. "The most important thing is for them to develop relationships with the rest of their platoon and fire team," he said. "When you're out here, it actually helps, because they are around each other 24 hours a day."

Many of the young Marines said they were glad to serve but were concerned that their inexperience could be a disadvantage when the war begins.

"In our world, getting combat experience is great news, so all of us were excited to get the Combat Action Ribbon. But I also wish I had a few more months to train," said Pfc. Steve Cimicata, 19, of St. Louis.

The unit's sergeant major, Henry Bergeron of Woonsocket, R.I., tells the recruits they are "lucky to be here" and that, despite their inexperience, they will be fine. He has spent 24 years in the Marines but has never fought in a war. He said he almost retired last year, but jumped at what will likely be his last opportunity for combat.

According to the battalion's commanding officer, Lt. Col. Christopher Conlin, 44, of Falls Church, the relative youth of his Marines also means they are among the most committed.

"Most of our guys joined after 9/11 and knew exactly what they were getting into," he said. "Everyone knew it when they signed on they'd be brought to the fight, and many of them joined because of the terrorist attacks. For these guys it is personal."

Pfc. Travis Harless, from Bakersfield, Calif., went to see a Marine recruiter on Sept. 12, 2001, intending to enlist. He was only 16, so the recruiter told him to wait a few months and get his parents' permission. He returned on his 17th birthday, permission form in hand.

"If it hadn't been for the attacks, I'd be in junior college or working in some part-time job right now," said Harless, now 18. "That one day gave me direction. It's not easy being the new guy, but I am doing the best I can to learn fast."

For specialized units, being the new guy is particularly hard. "We have two Marines who joined straight out of boot camp two weeks before we came here," said Lt. Kendrick Neal, the commanding officer of the battalion's scout sniper platoon. "But we don't work on the basics out here, only advanced stuff. So they are helping out as my radio operators."

There is a lot to learn and not much time. One new Marine who asked not to be identified said he wandered around camp for an hour one day looking for the chapel services and never found them. Many said they were figuring out the acronyms and abbreviations that are the language of military culture. Another said he always forgets the name of his platoon commander.

The responsibility for getting the new Marines up to speed on how the unit functions -- and the mission that could lie ahead -- is often left to the noncommissioned officers in their platoons, many of whom are no more than 22 but have been in the Marines for a couple of years. To integrate newcomers into the unit quickly, they sleep in large tents with their platoons, with their sleeping bags placed next to the other members of their 12-man squads. Cimicata, an assistant machine gunner, sleeps next to the corporal he will have to replace if that corporal becomes a casualty.

"It's a lot harder to train new Marines than old Marines," said Lance Cpl. Eric Douglas, 21, of Miami. "You have to teach them everything. They lose things. They break things. Coming right out of boot camp, they have to put their trust in guys like me."

The occasional practical joke helps break the ice, Douglas said. "Guys will ask them to go find the Humvee key, when Humvees don't have keys," Douglas said. "One time we asked for volunteers to be in-flight technicians on a TOW missile."

The commanders who will lead them into battle say that war has always been a young man's business and that if there is a conflict with Iraq, it will not be an exception.

"There's a reason why they call it the infantry," said Maj. Gen. James Mattis, who commands the 1st Marine Division, with the emphasis on "infant."

Marines drill in the Kuwaiti desert, where some arrivals are fresh from infantry training. Commanders say they appreciate having time to prepare.Marines from the 1st Battalion, 4th Marine Regiment waited for incoming helicopters in northern Kuwait last month.