Leckie was born on December 18, 1920, in Philadelphia, Pennsylvania. He grew up in Rutherford, New Jersey. He began his career as a writer in high school, as a sports writer for ''The Bergen Evening Record'' in Hackensack, New Jersey.

On January 18, 1942, Leckie enlisted in the United States Marine Corps.He served in combat in the Pacific theater, as a scout and a machine gunner in H Company, 2nd Battalion 1st Marines Regiment 1st Marine Division (United States). Leckie saw combat in the Battle of Guadalcanal, the Battle of Cape Gloucester, and had been wounded by blast concussion in the Battle of Peleliu. He returned to the United States in March 1945 and was honorably discharged shortly thereafter.

Following World War II, Leckie worked as a reporter for the Associated Press, the ''Buffalo Courier-Express'', the ''New York Journal American'', the ''New York Daily News'' and ''The Star-Ledger''. He married Vera Keller, a childhood neighbor, and they had three children: David, Geoff and Joan According to Vera, in 1951 he was inspired to write a memoir after seeing ''South Pacific '' on Broadway and walking out halfway through. He said "I have to tell the story of how it really was. I have to let people know the war wasn't a musical His first and best-selling book, ''Helmet for My Pillow'', a war memoir, was published in 1957. Leckie subsequently wrote more than 40 books on American war history, spanning from the French and Indian War (1754–1763) to Operation Desert Storm (1991). Robert Leckie died on December 24, 2001, after fighting a long battle with Alzheimer's Disease.