First Lieutenant Sidney Diamond was born to Russian Jewish immigrants in the Bronx, New York. He attended Stuyvesant High School, a school for intellectually gifted boys. Upon graduation, in 1939, he entered City College to study chemical engineering and became a member of the Alpha Phi Omega fraternity.

First Lieutenant Diamond entered into the U.S. Army as a private on 24 April 1942. Upon completion of basic training, he traveled to Edgewood Arsenal, Maryland to join the Chemical Warfare Service (CWS). He would train with Golf Company, 2nd CWS Training Battalion. After completing Officer Candidate School, he was assigned to the 82nd Chemical Battalion, Delta Company as a platoon leader.

The 82nd was attached to the 40th Division, 1st Battalion, 160th Infantry in the Pacific Theater of Operations. On 29 January 1945, acting as a forward observer, First Lieutenant Diamond successfully directed mortar fire during the initial stages of the action, killing and wounding an estimated reinforced platoon of Japanese. In order to bring fire upon other enemy positions, with heroic disregard for his own safety, he made his way alone under intense hostile machine gun, mortar and rifle fire to a position 150 yards beyond friendly lines. Despite continued heavy fire he remained in this position and skillfully directed his mortars in destroying many Japanese troops and strong-points until he was killed by an enemy shell.

First Lieutenant Diamond was awarded the Silver Star for his actions.