John Basilone was born to first-generation Italian immigrants Salvatore and Dora Basilone in Buffalo, New York, on 4 November 1916. He joined the Army in February 1936, spending much of his enlistment with the 31st Infantry in the Philippines before returning to civilian life on 7 September 1939.
Basilone enlisted in the Marines in July 1940 and was assigned to the 1st Battalion, 5th Marines at Quantico, Virginia, where he manned a Browning water-cooled .30-caliber M1917A1 machine gun with the heavy-weapons outfit, Company D. His prior service earned him the nickname, "Manila John." On 1 January 1941 he became part of the newly created 1st Battalion, 7th Marines (1/7). By the autumn of 1941 a new commander had taken over the battalion, a highly decorated veteran of the Banana Wars named Lewis B. "Chesty" Puller.