TOKYO — Fifteen years ago, a young LIFE magazine photographer named David Douglas Duncan caught the weary, mud-spattered face of a young U.S. Marine sergeant as he ducked enemy fire and slogged past a dead north Korean on the banks of the Naktong River.

It was a dramatic shot.

The young sergeant moved along at a lopsided run, his rifle dangling at his side, a hand thrust before him to clear his way through hip-high grass. The enemy soldier at his feet might have been a piece of crumbled refuse.

This was a perfect shot of the two most common beings on a battlefield — the quick and the dead. But the next morning, the young sergeant was dead, too.

His face, combined with others — the faces of agony, superhuman effort and violent death — gave the American public thousands of miles away a stark and graphic picture of a costly battle. They were to appear first in the pages of LIFE and later in Duncan's celebrated, best-selling book, "The Face of War," a collection of grisly photographic vignettes ranging from the Pusan Perimeter to the frozen mountain ranges along the Yalu River.

It made Duncan. one of the most celebrated war photographers of his time and ranked him only beneath the late Robert Capa as the most professional and accomplished.

Duncan has known may other faces besides that of the young sergeant. There are the Greek partisans, French poilus and Vietnamese peasants.

There is the solemn face of a Japanese general signing surrender documents aboard the battleship Missouri, and the broad and sensitive face of Spanish painter Pablo Picasso. Duncan, who quit LIFE in 1956 to live along the French Riviera and freelance, is the only photographer who has ever cracked the wall of seclusion around Picasso. The 85-year-old recluse allowed Duncan to photograph his work, home and family life, and to trace his life story through color pictures of his paintings, charcoal drawings and sculptures.

"That was really hard, man-killing," recalls the 50-year-old Duncan, who is graying at the temples but still appears fit and youthful.

"I photographed 100 pictures five times each. It was much harder than photographing people."

He used a high precision Alpa reflex camera, with multiple flash attachments, in total darkness. This was to eliminate glare and reflection and get the most vivid lines and colors.

The project damaged Duncan's eyes — "not permanently, I hope" —and he now wears glasses some of the time.

"Picasso himself is so dynamic and provocative a person," says Duncan, who did two books on the artist, "that you can't miss. I went right into his studio with him as he worked. He was never on camera. Nothing was ever set up. He worked as though I wasn't there. Oh, yes, in a war your subject and drama are there, also. You can't miss there, either — if you can stay alive."

Duncan brokee away briefly from Picasso, his neighbor on the Riviera, to go to Moscow and photograph art treasures in the Kremlin — another landmark in his travels as a photographer that began while he was a freshman at the University of Arizona 30 years ago.

He is now compiling his pick of thousands of photographs — people, places, faces and events — into a 450-page photographic biography — "the biggest anyone has ever done of his own work."

"I want to show 30 years of the generation that changed the world," Duncan says. "I landed here a Marine lieutenant and took color pictures of the surrender after I got shots of Tokyo, bombed out and burned down. I have pictures of the Indochina War that show the agony of the Vietnamese people and the French soldier."

There are also pictures of the Greek Civil War and of the revolt that broke the British mandate on Palestine — and of great personalities and priceless treasures. The book, "Yankee Nomad," has taken Duncan five years to compile. He was briefly in Tokyo, en route to New York, to explore the possibility of having the book printed here.

"It's scheduled for publication in October," Duncan says, "and I'm a prisoner of the book until it's finished."

Duncan says he may go to Vietnam after that. A television producer wants him to take pictures that show "high drama at the precise moment."

These would be flashed across the screen in quick succession, one after the other, for dramatic effect.