John S. D. Eisenhower, son of former President Dwight D. Eisenhower, died Saturday at the age of 91.

John Sheldon Doud Eisenhower lived on Maryland’s Eastern Shore in the community of Trappe. In a statement, his family gave no cause of death.

Defense Secretary Chuck Hagel called John Eisenhower “a true patriot” and praised him as “an accomplished soldier, diplomat and author.”

John Eisenhower was born in Denver on August 3, 1922, the second son of Dwight D. Eisenhower and Mamie Doud Eisenhower. Their first child had died of scarlet fever the year before at age 3.

He grew up as his father rose in the ranks of the Army. During World War II, the senior Eisenhower became supreme commander of Allied Expeditionary Forces in 1943 and then general of the Army with five-star rank. Dwight D. Eisenhower was elected president in a landslide in 1952 and again in 1956.

John Eisenhower was the second son of Dwight D. Eisenhower and Mamie Doud Eisenhower

Both father and son graduated from the US Military Academy at West Point, the son on June 6, 1944 – the day his father oversaw the Allied invasion of Europe. He spent 35 years in the Army, including 19 years on active duty and several years in the Reserve. He retired with the rank of brigadier general.

John Eisenhower taught English for three years at West Point, then volunteered for service during the Korean War and later became a battalion commander.

He served on his father’s White House staff for the last few years of his administration and later helped his father write his post-presidential memoirs. The younger Eisenhower began writing his own books, then served as US ambassador to Belgium during the first years of the Nixon administration. He soon returned to writing, focusing on the military’s relationship with government and politics.

His marriage to Barbara Eisenhower ended in divorce.

John Eisenhower is survived by his second wife, Joanne, and his four children: daughters Anne, Susan and Mary, and son David, who married President Richard Nixon’s daughter Julie.