Dodging Friendly Fire

Iraqi tanks perched on the north side of a sand ridge near the Saudi-Kuwait border were firing at a company of U.S. Marines on the south side. The Marines were returning fire with TOW antitank missiles. Overhead, a U.S. Air Force A- 10 Thunderbolt swooped toward one of the Iraqi tanks and released a heat- seeking Maverick missile.

But instead of flying straight for the target, the missile was diverted by the hot exhaust of a Marine light armored vehicle that stood between the U.S. plane and the Iraqi tank. The Maverick smacked into the left rear side of the LAV, blowing up the vehicle and killing all seven Marines inside.

The tragic exchange was one of the first engagements of the ground war, an opening volley in the 36-hour battle of Khafji. It also represents this war's first documented case of U.S. casualties from "friendly fire" -- a combat euphemism for troops' getting shot, shelled or bombed by their own side.

Friendly fire bedevils every war. Many World War II veterans recall running for foxholes whenever U.S. planes approached. In one of the worst cases on record, the Eighth U.S. Army Air Force bungled the bombing of enemy lines shortly after D-day in Normandy. Their explosives hit the Army's VII Corps, killing more than 100 soldiers and wounding 500. As in other such incidents, the G.I.s on the ground tried to defend themselves by firing back at their own planes.

The U.S. armed services have developed elaborate -- albeit imperfect -- systems to avoid friendly fire. To prevent mishaps like the one near Khafji, Marine air-support planes carry laser-guided versions of the Maverick missile that must be guided to their targets by the pilot. Though not as smart as the infrared models favored by the U.S. Air Force, which can be fired and left to track the target on their own, the laser-guided Mavericks are less likely to mistake a friend for a foe.

Warships and attack planes carry electronic ID systems, like the IFF (Identification Friend or Foe) radio transponders that are standard equipment on military and civilian aircraft. A missile battery equipped with IFF can "interrogate" an aircraft by beaming a radio signal at it and listening to the answering squawk. But the system is not foolproof. In the 1973 Arab-Israeli war, Arab batteries fired 2,100 antiaircraft missiles and destroyed 85 aircraft -- 45 of them Arab, 40 Israeli.

Since IFF transponders are impractical for ground forces, aircraft flying close support stay in constant radio contact with forward air controllers, whose job it is to track the shifting battle lines and point out enemy targets. Before an attack plane can launch its missiles at a Iraqi tank, an FAC must identify the target, declare that particular plane "hot" and switch on the targeting authority on the plane's computer. "The complexity is that you've got human beings in the chain," says Army spokesman Major Peter Keating. "And at night, when everybody's moving and talking on the radio, there's no guarantee that everyone's in the right place at the right time."

No one knows that better than General Norman Schwarzkopf. Not only was he once bombed by U.S. B-52s in Vietnam, but he was the commanding officer of a young Iowa farm boy, Michael Mullen, whose death by U.S. shelling became the subject of C.D.B. Bryan's 1976 best seller, Friendly Fire.