John Eisenhower, 91, a soldier, diplomat, and acclaimed historian who was the only surviving son of President Dwight D. Eisenhower, died Saturday at his home in Trappe, on Maryland's Eastern Shore.

His daughter Susan Eisenhower confirmed the death, but no cause was immediately known.

A graduate of West Point, like his father, and the holder of the rank of brigadier general, John Eisenhower was ambassador to Belgium and a prolific author of history and biography books.

He published books on World Wars I and II, the Civil War, and the Mexican War. Praise came his way early for The Bitter Woods, on World War II's Battle of the Bulge.

He had just completed a book on William Sherman, the Union Civil War general.

One of his subjects was his father. General Ike: A Personal Reminiscence offers personal glimpses of the relationship between his father and such world figures as Winston Churchill and Charles de Gaulle.

John Sheldon Doud Eisenhower was born Aug. 3, 1922, in Denver, where his mother, Mamie Eisenhower, lived.

After a peripatetic childhood, he was a member of an accelerated wartime program at West Point, graduating on June 6, 1944 - by coincidence, the date of the Allied invasion of Normandy presided over by his father. Part of the new lieutenant's graduation leave was spent in Europe as an aide to his father.

The next month, he went to infantry school at Fort Benning and in October was assigned to the 71st Infantry Division, which was later sent to Europe.

After service in postwar Europe, he was assigned to teach English at West Point and received a master's degree from Columbia University.

As a major, he saw combat with the Third Infantry Division during the Korean War in 1952 and 1953. He received the Combat Infantryman's Badge and the Bronze Star.

After holding a variety of Army posts, he went to the White House as assistant to one of his father's top aides, Gen. Andrew Goodpaster. After his father's term ended, he took leave from the Army to help his father write three books. He left the Army in 1963.

He went into the Army Reserve and became a brigadier general before retiring.

His first marriage ended in divorce. Survivors include his second wife, Joanne, and four children from his first marriage, Anne, Susan, Mary, and David, an author, public policy fellow, and professor at the University of Pennsylvania who is married to Richard Nixon's daughter Julie.