© David Douglas Duncan, ca. 1950, Korean War

"This," Duncan told LIFE.com of a picture made during the fight for Seoul, “is the best picture I made in Korea of civilians — a family running down stairs, a father holding a baby, tanks firing away. Those tanks are taking fire from North Koreans right down the street.”

On the anniversary of the start of that brutal, often savage conflict, LIFE.com presents a gallery of Duncan’s celebrated pictures from America’s “Forgotten War.”

From the hellish heat of summer to the arctic freeze of winter, Duncan traveled with Marines, documenting the grinding, torturous lives they led — and that troops everywhere have always led — in war zones the world over.

While recalling the unspeakable violence and gnawing deprivation (no warmth in winter, no relief from the heat in summer, hunger all the time) of those years, Duncan makes a point of praising the Americans’ South Korean allies. "The thing that comes to mind right away, right now, when looking at these pictures again," Duncan says, "is that at no time — at no time — did any Marine feel he had to look around to see what the South Koreans were doing behind him. The Marines in Korea never feared ‘friendly fire’ or artillery coming from the South Koreans — from their allies — like they did later in Vietnam, fighting with the South Vietnamese. The Koreans could be trusted."

The Korean War lasted for roughly three years, from June 25, 1950 — when North Korea invaded the South — until 1953, when the United Nations Command, the North Korean People’s Army and the Chinese People’s Volunteers signed an armistice agreement. However, the South Korean president, Syngman Rhee, refused to sign the document — meaning that, technically, North and South Korea have been at war for the past six decades. (read more)

» find more war & conflict photography here «