The typical American soldier in the Persian Gulf is 27 years old, six years older than the average in Vietnam, and more likely to be married and have more children, factors that military analysts say could have important implications for the performance of U.S. troops.

Because there is no draft forcing thousands of 18- and 19-year-olds into the Army, and because one-fifth of American troops are reservists who tend to be in their thirties or forties, the U.S. force in Operation Desert Storm is the oldest to fight since the Civil War.

The aging of the armed services has led to a debate including Pentagon officials and private analysts about how the older force will perform in wartime.

U.S. troops in the four major wars of this century have been mostly single, young fighting men without family worries. Whether older, married soldiers with children are more "risk-averse" and less effective is a worry for some military planners.

On the other side of the issue are those who believe that mature, experienced soldiers are more capable of operating the high-tech equipment that is the heart of America's gulf war effort.

"It used to be said that you could tell how many dependents a pilot had by the altitude he pulled out of a strafing run," said Martin Binkin, a military manpower expert at the Brookings Institution. "For centuries, we have taken young, single males into combat" because it was believed they could be "molded better and take more risks" than older soldiers, he said.

Speaking officially, the Pentagon says it is unsure whether the fact that its troops are older and more likely to have families will change how well they fight.

"What effect age will have on the fighting force, we don't know," said Maj. Douglas Hart, a Pentagon spokesman. "What effect the higher marriage rate will have on the force, we don't know."

But several consultants under contract to the Pentagon say military manpower officials are watching the gulf war carefully because they view it as a test case of how well America's older fighting force will do its job.

The percentage of married military personnel rose from about 40 percent in 1970 to 60 percent in 1990, and the average number of dependents increased from one to almost two, according to the Defense Department.

"Before and during Vietnam, the point of view was that if the Army intended for you to have a wife, the sergeant would have issued you one," said Maj. Gen. Fred F. Marty, commander of the Army's Community and Family Support Center. "Child-care concerns were almost unheard of in Vietnam. There has been significant change."

For the reservists, who are generally older than the active-duty personnel (the average age of an Army reservist is 28.5 years and average age for reservist officers is 38), the Persian Gulf mobilization meant an "unprecedented uprooting of older people," said Peter A. Morrison, a demographer who has studied the Army for the Rand Corp. think tank.

Many of them had difficulty adjusting and had not made plans for child care or for dealing with financial difficulties at home, Pentagon officials say. The "weekend warriors" also are having greater adjustment problems in the war zone, after being plucked from civilian jobs and abruptly forced to trade a double bed in a split-level house for a cot in the desert.

"At combat levels, we have always wanted young, single guys unencumbered with family concerns," said Charles C. Moskos, a military sociologist at Northwestern University. "It's worst for the single parents."

A soldier with family problems is "going to be thinking about how to get home, more likely to get sick and more likely to have his mind on other things," he said.

If the gulf war results in many casualties, deaths among today's force also would leave more widows and widowers, and more children without a mother or a father.

"It will be interesting how these casualties play back at home," Moskos said. "It's going to affect the military bases where the families are, with some devastation."

Other experts argue that the older average age means that the fighting force has never been as productive and highly trained. During the Vietnam draft, soldiers often served two years, five or six months of which were spent in training if they were needed for a specialty job.

Now, nearly double the proportion of enlisted personnel have 10 or more years of experience, compared with the Vietnam era.

David W. Grissmer, a military manpower expert with the Rand Corp., said that because about two-thirds of military personnel operate in noncombat support roles, their older age and longer experience is a clear advantage.

"Especially in the high-tech jobs, like manning the Patriot missile or the more sophisticated weapons, you want people who have been there a long time," he said.

If there is a ground war, those in the front lines are likely to be younger soldiers.

"Those who are going to die will likely still be the young," Grissmer said. "The people in the jobs where there is the great risk -- the tank crewman, the infantry -- are all young."

The transformation from an Army of young bachelors to an older, married force has sent the Pentagon scrambling to deal with a whole new set of responsibilities: child care, family health, and the financial and psychological problems caused by the massive deployment to the Middle East.

The aging force also is costing billions of dollars more than the traditionally younger armed services.

A 1987 Congressional Budget Office report estimated that the "sharply rising percentages" of enlisted military personnel with 10 years of experience would cost an additional $2.3 billion between 1988 and 1992.

Along with a much higher pay scale for more senior personnel, retirement costs are exploding. With more soldiers staying in the service for 20 years or more, more are eligible for retirement benefits. For every billion dollars spent on military salaries, an additional $430 million goes for those benefits. The military also faces higher costs because more soldiers have spouses and children than 20 years ago.

"The more senior force is more expensive, even though you save some in training" and need fewer people because of increased productivity, said Richard Fernandez, a national security analyst at the budget office who has studied the issue.

An extreme example of the aging military is 63-year-old Lorain Kuryla, who left the suburbs of Chicago for the Persian Gulf with her Air Force reserve unit in September.

After saying goodbye to her five grandchildren, the white-haired Air Force Reserve master sergeant, known as "Grambo," worked 12 hours a day, every day for a month, as a personnel official with the 928th Tactical Airlift Group.

"There were a couple of days, when the chemical warfare training was increasing and we thought any minute there might be an attack," said Kuryla, who is still on reserve duty but has returned to her unit's Chicago base. "I got a little teary and I thought: 'Look where you're at. You're 63 years old.' "