With just a week until Soviet troops formally leave Afghanistan, a familiar drama is unfolding. Only the names have changed, with John and Jim giving way to Yuri and Vladimir.

In April 1975 the scenes were of Americans, mainly diplomats, plucked from the roof of their embassy in Saigon by helicopters.Fourteen years later, helicopters again are in the air providing protection for departing transport planes. This time they are taking Soviet troops home from Kabul.

Both superpowers have left the stage to the boos of some of their own people, their international reputation scarred by interference in what many historians judge to be civil wars.

They have learned from their forays into Vietnam and Afghanistan that there is only grief for them in such large-scale interventions, says Professor Gabriel Kolko of Canada's York University History Department.

"There is a Vietnam syndrome and there is an Afghanistan syndrome. They'll never do it again," he said.

About 15,000 Soviet soldiers died in Afghanistan. Nearly four times as many American soldiers were killed in Vietnam.

In the hospitals of the United States and the Soviet Union, thousands of maimed young men relive the nightmares of terrible wounds in the rice paddies of Vietnam and the high passes of Afghanistan.

Many, many more Afghans and Vietnamese died on the soil of their own homeland, killed by each other and the troops of the superpowers.

Judging from the U.S. experience, much of the Soviet Union's agony is still to come.

"The Afghan war will have a greater meaning for the Soviet people in 10 or 20 years than it has now," says Mykola Movcham, a Soviet soldier who defected after serving for a year as a sergeant in a unit south of the Afghan capital, Kabul.

Drugs, alcoholism and a hopeless cynicism that followed many GIs back to the United States already is being reported in the Soviet Union.

Movcham, who has lived in New York for the past four years, told Reuters he feels a kinship with the American veterans of the Vietnam War.

He could be one of many American draftees talking about the Viet Cong when he describes his mujahideen foe.

"The rebels were very tough with high morale. Whatever else they can do, I don't know - but they can fight," he says.

The sound and lighting of the final days of the U.S. and Soviet adventures seem the same.

Television reports from Afghanistan show rockets, helicopters and planes. They broadcast defiant voices of hope, the carefully chosen words of diplomats, the anger of refugees, the babble of uncertainty.

Reuter correspondent Bernard Edinger was there for the April 30 fall of Saigon.

He recalls: "The North Vietnamese regulars and often-barefoot Viet Cong guerrillas who took over the city appeared completely disoriented by the modern aspects of Saigon and by its vast size.

"North Vietnamese officers halted their units' progress and pored over tourist maps at street corners while asking for directions. Some of the country-bred teenage Viet Cong fighters readily admitted they had never seen buildings more than a story high."

Edinger says the communist high command was surprised by the speed of its victory. Top commanders did not come to Saigon until a week after the city fell, and they took several more weeks to organize its control.