SAN DIEGO (AP) _ Retired Brig. Gen. John Groff, a World War I hero and the Marine's oldest surviving general, has died of a heart attack at age 100.

Groff died Tuesday at Oceanside's Tri-City Hospital, Kathie Graler, the service's historian at Camp Pendelton Marine Corps base, said Thursday.

''He was the grand old man of the Marine Corps,'' said a family friend, Lance ''Dutch'' Parker, a retired Marine chief warrant officer whose late father, David ''Whitey'' Parker, served with Groff.

Graler said Groff had been the oldest surviving Marine general and the last member of the World War I Lodge in Oceanside, about 45 miles north of San Diego.

Born in Syracuse, N.Y., in 1890, Grof enlisted in the Marines in 1912. He was a gunnery sergeant and patrol leader when his unit fought in France in the Battle of Belleau Wood, one of the bloodiest and most storied battles in the Corps' history.

Groff was wounded in the battle, which stopped a German push toward Paris. He was awarded the Navy Cross, the Distinguished Service and the Purple Heart and promoted to second lieutenant.

''We didn't realize we were going to get shot like that,'' Groff said in a newspaper interview earlier this year. ''We lined up and went into the woods, and then all hell broke loose.''

Promoted to major in 1938, Groff became commanding officer of the Marine Corps Recruit Depot in San Diego, a post he held for six years, helping train Marines who would fight in World War II.

Groff participated in the 1942 dedication ceremonies opening Camp Pendleton and in recent years was frequently guest of honor at Marine Corps ceremonies.

Groff retired in 1946 and was promoted from colonel to brigadier general for his distinguished service, Graler said.

He worked for Hughes Aircraft Co. and Douglas Aircraft Co. during the late '40s and early '50s. He moved to Oceanside in 1969.

Groff is survived by daughters Mildred Ann Hanson of Bothell, Wash.; Pauline Ethel Ralston of Victorville, and son John Louis Groff of Poway.