ABOARD THE USNS COMFORT, PERSIAN GULF, NOV. 7 -- As a Navy doctor, Cmdr. Gage Ochsner spent the last two years patching bullet holes in the victims of Washington's drug wars.

That training, which qualified him as one of the Navy's most experienced trauma surgeons, has earned him a new assignment: directing casualty operations aboard this mammoth, Baltimore-based hospital ship, should war come to the Persian Gulf.

While the United States is amassing more than 240,000 troops in the region to counter Iraqi aggression, military officials are struggling to assemble the medical means to treat thousands of men and women who could be wounded should combat result.

{Meanwhile, at U.S. military hospitals in Frankfurt and Wiesbaden, Germany, doctors already are treating more than 1,100 servicemen flown in from Saudi Arabia for problems ranging from orthopedics to the psychiatric. Story on Page A63.}

Even as the United States dispatches some of the most sophisticated medical equipment in the world to the distant Persian Gulf region, military authorities raise concerns over the psychological toll on doctors, nurses and corpsmen who have never experienced the trauma of combat medicine. Military estimates of combat casualties, should war occur, range from 5,000 to more than 30,000, depending on the length and type of battles waged.

"I don't think anybody is prepared for the hundreds of casualties we're going to see" on this ship, said Ochsner, 36, of Arlington, who would direct casualty triage operations aboard the Comfort during combat. "I worry about the nurses and corpsmen who haven't seen it. It's horrible to look at, it's nasty, people are screaming and you smell blood everywhere -- it's an overwhelming assault on the senses."

The military, concerned over shortage of combat-experienced doctors in the 20 years since the Vietnam War, recently began lending young doctors like Ochsner to urban hospitals hard hit by outbreaks of drug-related shootings. The program offered military doctors training in treating bullet wounds and other warlike traumas, while helping short-staffed urban emergency rooms. The Washington Hospital Center was among the first civilian hospitals to participate.

In his first year at the Washington Hospital Center's Medical Stress, Trauma and Resuscitation (MEDSTAR) unit, Ochsner, a third-generation doctor of his native New Orleans family, said he treated 300 patients for bullet wounds. If war erupted in the Persian Gulf, the U.S. military could suffer that many casualties in the first minutes of ground combat with heavily armed Iraqi forces.

Since President Bush ordered U.S. troops to Saudi Arabi in early August, the military has rushed dozens of mobile hospitals with thousands of patient beds to the area.

Almost 70 percent of the medical staff of the Bethesda Naval Hospital is on the Comfort, a tanker that in 1987 was converted into a floating hospital with 1,000 patient beds and 12 operating rooms. Its sister ship, the USNS Mercy, is also in the region. According to Navy officers, the ships rank as the ninth largest hospitals in the world.

Even with the two ships and dozens of tent hospitals spread throughout the Eastern Province of Saudi Arabia, military authorities say they are concerned that they could fall short of hospital space in the event of war.

The threat of chemical weapons also concerns medical officials. Ochsner noted that the Comfort has three chemical decontamination units. Each cell can take one patient and each patient could require up to 15 minutes to be decontaminated. Even though the ship could handle a few additional patients, a large number of casualties could result in a massive bottleneck of suffering patients.

For most of the naval medical personnel aboard the Comfort, this has been their first sea deployment, and for virtually all, their first potential combat mission. The transition has not been easy, either professionally or personally

The Navy has dispatched teams of psychological counselors to assist the staff in adjusting to both the physical inconveniences of their new jobs and the emotional anxiety of facing potential massive casualties.

Within a matter of days last August, the operating rooms, nurse stations and laboratories of the Bethesda hospital were emptied into the ship at its berth in Baltimore. Staff members found themselves in new jobs and working with colleagues they had never before met.

They describe the first days at sea as a din of noise and confusion. There was no telephone system or telephone directories for the ship, which is three football fields long and 10 stories tall. Staffers communicated via the ship's crackling intercom system before they could put a switchboard and phone network in place.

"You're limited in resources on the ship -- both with supplies and personnel," said Cmdr. Barbara Vernoski, 39, of Rockville. "We've never done anything like this before."

But even more difficult for the more than 1,000 men and women aboard the ship is the personal adjustment from suburban Washington comforts to shipboard life with little privacy, few diversions and no indications of when they will return home.

They conduct aerobics classes on the helicopter landing deck and have formed chess clubs, bridge clubs and needlepoint circles. They devour movies loaned by a Washington video club. They lift weights in the ship's tiny gym.

The biggest morale booster aboard the Comfort is the ship's radio operator, who has managed to link up with ham radio operators across the United States, allowing crew members to connect with the telephone system and make collect calls home.

Patients, too, find life different in this floating hospital, where the operating table is chained to the floor during high seas and the injured are strapped to their beds. Patients do not lie idle, however. "We expect patients to help with the cleaning and mopping and folding the linens," said Cmdr. Pat Bull, 38, of Silver Spring, a nurse in the orthopedics ward. "At Bethesda, we'd never ask a patient to do that."

Thus far, the patient load has been light, with about 200 troops from all of the services trickling through the hospital since it arrived in mid-September. Many of the injuries have been sports-related as troops attempt to keep fit by jogging, wrestling or playing football.

About 15 percent of the patients have suffered emotional and psychological problems, according to Capt. Roger Pentzien of Vienna, Va., commander of the hospital ship medical staff.

The ship experienced its first serious casualties -- and deaths -- last week after a mishap aboard the amphibious landing ship USS Iwo Jima. Six crew members of the Iwo Jima died immediately when they were hit with 850-degree steam from a ruptured pipe in a boiler room. Four sailors were scalded over 90 percent of their bodies and helicoptered to the Comfort.

Despite 13 hours of intensive care in the burn unit, the four men brought here died. Hospital staffers became so emotional over the losses that the ship's mental health counselors and chaplain conducted numerous sessions with the nurses and medical staff of the unit.

"Some people felt like they didn't do enough when they died, even though we did everything we could," said Lt. Cmdr. Barbara Schmitz of Silver Spring, head of the burn unit. "It's different at home -- when they die they're 90. Here, I'm writing the ages -- 20, 22, 25 is the oldest."