This morning's surprise announcement of the deaths of eight Americans in an aborted effort to free the hostages in Iran marked the third time in recent years that similar U.S. operations have failed or led to heavy loss of life.

The planned mission inside Iran, called off because of equipment failure, recalled two operations mounted in Southeast Asia in the 1970s. The first was the attempt to pluck prisoners of war from the camp at Sontay, North Vietnam, in 1970. The other was the effort to rescue the crew of the freighter Mayaguez, seized off Cambodia in 1975.

The daring Sontay raid, carried out under cover of darkness in November 1970, proved fruitless when the airborne raiders found the camp empty.

Planners were guided by reports that as many as 70 Americans had been held at Sontay, 23 miles from Hanoi, with 100 North Vietnamese guarding them.

The picked team of raiders flew into Sontay by helicopter after several months of training that employed a scale model of the North Vietnamese camp.

Although no prisoners were found in the camp, the mission was otherwise smoothly carried out. Aided by shock and surprise, the Green Beret raiders had only one man wounded in the 1970 mission.

In 1975, when U.S. Marines made an assault intended to rescue the Mayaguez crew from a Cambodian island, the 40-man crew was recovered, but losses were greater. The operation cost the lives of 18 Marines who made the assault and 23 airmen whose helicopter crashed while on the way to the scene.

The operation inside Iran that was revealed in this morning's White House announcement also follows two other well-known, and more successful, hostage rescue missions carried out by other nations.

In a celebrated raid on July 4, 1976, Israel airborne commandos, flew thousands of miles to Uganda's Entebbe airport where they freed more than 100 hostages held by pro-Palestinian hijackers.

Israeli commandos landed in C130 transport planes to launch the now-legendary strike that achieved complete surprise, cost few Israeli casualties, and provided a great boost to Israel's morale.

The possibility of conducting a raid similar to that at Entebbe had been widely discussed in the United States since the hostages were taken in Tehran last November. Many observers had argued that conditions in Iran posed far greater obstacles than were faced by the Israelis.

One obstacle was that the hostages are being held at the U.S. Embassy, which is some distance from an airport.

It has also been asserted that those holding the hostages in Iran were better organized and supported, and less likely to be surprised.

In another successful and widely praised operation, a squad of West German antiterrorist commandos made a daring post-midnight surprise attack in Somalia on Oct. 18, 1977, to free 86 passengers and crew members aboard a hijacked Lufthansa airliner.

The commandos used a specially equipped Boeing 707 jet.