What's an Army general to do? He suddenly finds himself in command of an important operation that requires extensive help from the Navy and the Air Force, but he doesn't know anything about the Navy and the Air Force.

That problem is supposed to be solved by the National Defense University (NDU), a group of military colleges headquartered at Fort McNair that are supposed to teach the services how to work together. (The classic example of what the school is supposed to prevent was the ill-fated Iranian hostage rescue mission, a joint operation that featured Marine helicopters, Air Force airplanes, an Army commander, troops from all the services and serious command and control problems.)

NDU represents the elite of the military's instructional system. The university itself is only five years old, but its component colleges--the National War College, the Industrial College of the Armed Forces (both at Fort McNair) and the Armed Forces Staff College (at Norfolk)--have long traditions of dealing with issues and tactical questions that affect all the military services and diplomatic activities as well.

This year, the war college has 159 students in residence and the industrial college has 208. The staff college, which serves lower-ranking officers, has 550 students annually in two sessions. Correspondence and extension programs serve hundreds more.

Bruce Laingen, the senior American hostage in Iran, is the vice president of NDU--with the rank of ambassador--and about a third of the university's students are federal civilian employes, mostly from the Defense and State departments and the CIA.

The university, however, is now in the midst of a fundamental debate over whether it is fulfilling its mission in the best way. In the eyes of the university's board of visitors, instruction in the complex world of joint operations takes place at the wrong time--sometimes years before generals and admirals reach the rank where they need the knowledge and the personal contacts that come from 11 months of work together in classrooms and seminars.

A panel of the board has recommended that the university's program be changed to include such training for newly selected generals and admirals. The problem is that the change, as originally envisioned, would substantially alter and, under one scenario, eliminate the existing program the university has for colonels and captains, many of whom retire without ever winning stars or stripes.

The final decision will be made by the Joint Chiefs of Staff, who have the matter under active evaluation, according to a spokesman.

The board of visitors is heavily laden with retired generals and admirals plus a few civilians with military or diplomatic experience. The idea of a star-level supercourse stressing joint operations has been pressed most vigorously by retired Air Force Gen. Russell E. Dougherty, former commander in chief of the Strategic Air Command and a board member.

"When you get to be a general officer, people forget about education," Dougherty said in an interview. " . . . This business of providing a deterrent to war is just too complicated for any single service person or any single background. . . . I look back at what I know now and didn't know then when he was selected to be a general , and an instant exposure would have helped. I could have done a better job . . . ."

Dougherty's plan is radical in the context of military tradition: He would eliminate the present course for senior non-flag officers at the National War College and replace it with an 11-month supercourse.

"I'm talking about changing the character of the National War College to what I think it was intended to be by Eisenhower," Dougherty said. The National War College was created on Gen. Dwight Eisenhower's recommendation after he saw the problems of joint and allied operations during World War II. Previously, the senior command colleges had been the exclusive property of the individual services and each contained heavy servings of service--not joint--military doctrine.

The board of visitors, which can recommend but not order policy changes, went along with Dougherty's suggestion after meetings last summer.

But in a session last week, Air Force Lt. Gen. John S. Pustay, the university's president, persuaded the board to settle for a short course for generals that would fit into the existing National War College. To do what the board originally suggested, he said, would be "at the cost of disestablishing the National War College," and that is clearly something he does not want to recommend.

Now, with the board's blessing, Pustay has ordered a study of a shorter program for top-ranking officers.

The course the panel originally outlined contains subjects civilians would like to think their senior military commanders know. "This course," the panel said in its recommendation, "should focus on the current and projected international environment for U.S. national security, the domestic environment for decision-making, the management of national resources human and material , critical issues of national security policy and joint military strategy, doctrine and tactics . . . . Heavy stress should be placed on operational questions stemming from joint capabilities, limitations, procedures and problems . . . ."

None of the early papers on the establishment of a senior program includes cost estimates. The combined budgets of NDU's two Fort McNair colleges run about $8 million annually; the total Pentagon budget for individual training is $10.5 billion out of a total military budget approaching $210 billion.

A little extra education for generals and admirals, Dougherty argues, would be pennies. "It won't even fractionate," he said.