The military term is "friendly fire," one of the most durable euphemisms of combat. It means troops getting shelled or bombed by their own side. Military experts say it happens in every war.

In World War II, the United States lost two submarines to friendly fire -- one mistakenly bombed in the Caribbean, the other depth-charged by a destroyer in the Pacific. They went down with all hands.

In Korea, a U.S. Marine platoon was incinerated by a napalm bomb dropped on its position by an American plane. In his book, "The Forgotten War," military historian Clay Blair quoted one of the survivors, Pfc. James Ransome Jr.: "I don't know how in the world the flames missed me. . . . Men all around me were burned. They lay rolling in the snow. Men I knew, marched and fought with begged me to shoot them. . . . I couldn't. It was terrible."

In Vietnam, a young soldier from Iowa, Sgt. Michael Mullen, was killed by a stray U.S. artillery shell in an incident made famous after the war by C.D.B. Bryan's book, "Friendly Fire." Mullen's battalion commander was H. Norman Schwarzkopf -- then an obscure lieutenant colonel, now Operation Desert Storm commander.

If some U.S. Marines were killed by friendly fire in Saudi Arabia last week, as appears likely, Schwarzkopf and his colleagues will not be surprised.

"I've been bombed by our own Air Force," Schwarzkopf told reporters last Sunday in Riyadh, Saudi Arabia. "I was bombed by B-52s one time in Vietnam." There was no point in getting angry about it, Schwarzkopf said. It was not deliberate; it's just something that happens in every war.

"We're in combat right now," Marine Maj. Gen. Robert Johnston said at yesterday's military briefing in Riyadh. In combat, especially at night, "there will be other occurrences of some of our troops potentially being a victim of friendly fire," he said.

"If you look at the speed and the involvement of tanks against tanks, you're going to find that in the intensity of battle it is not easy to tell sometimes a four-wheeled vehicle from a six-wheeled vehicle. So I'm afraid these things are going to occur, I think, in a very active, hostile environment," Johnston said.

"It's happened in every war that I've ever heard of," retired Navy Capt. Edward L. Beach, author of "Run Silent, Run Deep," said yesterday.

He recalled the 1943 sinking of the submarine USS Dorado that while sailing through the Caribbean was bombed by a U.S. plane that mistook signal lights for muzzle flashes. The USS Seawolf was sunk in late 1944 by a U.S. Navy destroyer that ignored or misread identifying signals the submarine was sending by sonar.

In a paper prepared for a 1982 military history symposium at Carlisle Barracks, Pa., Army Lt. Col. Charles R. Shrader reported that there were 90 "friendly fire" incidents in the Vietnam War and 173 in World War II. The number of U.S. troops killed or wounded in those incidents is not known because the armed forces do not report such casualties separately from others incurred in combat.

The fighting that left 11 U.S. Marines dead near the Saudi-Kuwaiti border last week -- at close quarters, at night, and in partnership with troops from other armies that are physically and linguistically indistinguishable from the enemy -- was the type of fighting that can be expected to result in some friendly fire casualties, retired Army chief of staff John H. Wickham Jr. said yesterday. "There are a variety of reasons," he said, including bad weather and inaccurate target designation.

"If friendly units, heavily engaged, call in {artillery} fire for effect right against enemy forces on top or right in front, the firing units may not have time to deliver registration rounds to make adjustments. Inside a city, especially at night, patrols may not know exactly where they are, they may be a few hundred meters off. They may not have accurate street maps," he said.

He said U.S. troops are trained in "vehicle identification" -- they know how to distinguish their tanks and armored personnel carriers from the other side's -- but darkness, dust, fear and the presence of allied units that may have different types of equipment may create confusion.

U.S. artillery fire "injured soldiers in my battalion in Vietnam," Wickham said. "Every commander has had the experience."