American television viewers saw film clips of the U.S. Marine guards succumbing to the Tehran mobs without firing a shot in resistance. But those embassy guards "accomplished their mission," according to their commander, by holding off the Ranian demonstrators long enough to destroy the embassy's code machines and other secret material.

"This was not like the Pueblo," said Col. James L. Cooper in a reference to the Navy spyship North Koreans captured in 1968 before the crew could destroy her secrets.

Cooper, who commands the 1,100 Marines guarding U.S. outposts in Iran and 101 other nations, provided an insight into what the government is up against in turbulent Third World countries.

Cooper said security of U.S. outposts "is predicated on the assumption the host government will fulfill its responsibility under international law of protecting diplomatic missions -- not only ours, but everybody's."

Marines guarding U.S. embassies in a crisis are "supposed to conduct delaying actions to give the embassy time to button up; to evacuate some personnel and move others to safe havens -- And to give the host government time to react," Cooper explained.

It has worked out that way, Cooper said, in recent demonstrations at U.S. embassies in Bonn, San Salvador and Beirut. In each case, the host government's security force came to the rescue.

"We're not going to maintain our missions by force of arms," he said. "Physically, we couldn't do it" with the Marine guards available. This means, he said, that "when the host government isn't going to protect an embassy, you can no longer guarantee the safety of the people there. The Marine Corps can't take up the slack."

Turning to the U.S. embassy in Tehran specifically, Cooper said it would have taken at least a battalion of about 800 combat Marines to protect the 27-acre compound, which abounds with natural cover for terrorists.

Cooper said that on Nov. 4, the day of the takeover, three Marines were manning their assigned posts. One was inside the control booth in the entrance of the embassy, a second was patrolling inside the building and the third, was guarding the ambassador's residence. Ten other Marines were off duty at the time.

Cooper said that about 3,000 unarmed Iranian demonstrators started milling around outside the U.S. embassy.

The demonstration gradually grew in violence, Cooper said. State Department officials said that they had reduced the embassy staff to a minimum before the takeover, had strengthened the doors and had taken other measures, out of concern lest violence arise.

As it became apparent that the demonstration was bent on violence, Cooper said the Marine guards fired tear gas to show their advance. Washington officials learned through a phone connection with the embassy, the colonel continued, that code machines and related equipment were about to be blown up in the "C and R" room in the embassy with thermite charges.

"We're going to do it," is what the officials heard before the phone connection was broken, Cooper said. "I'm confident the Marines accomplished their mission by buying time" to allow this destruction of sensitive material, he added.

Each of the three Marines guarding the embassy in Tehran had access to a 12-guage, pump shotgun loaded with five shells containing 27 pellets of No. 4 shot. The Marines also carried .38 caliber pistols and had cannisters of tear gas.

"A Marine guard is trained never to draw his weapon unless he's going to fire it," said Cooper. "The minute a weapon comes out of the holster it is supposed to be smoking."

The decision on whether to fire at the crowd was up to the State Department security officer on duty that day at the embassy, Cooper said. He decided against shooting at the unarmed crowd of 3,000, the colonel continued.

Cooper said those advocating an attempt to rescue the American hostages in Tehran do not appreciate the difficulties nor the risks involved.

For one thing, he said, there is no place nearby from which to launch a surprise attack.

"If you're going to go in there in force, you're going to war," Cooper said. "The question then becomes whether it's worth jeopardizing the lives of the hostages and the rescue party."

Asked if the Marine Corps could not duplicate the Israeli rescue at Entebbe, Cooper replied: "I didn't say we couldn't do it. I asked, 'Is it worth it?' Tehran is a long way from anthing. The only thing that's close is the Soviet Union. Perhaps we should call on their good offices."