Benjamin Nathaniel Ahl was born in Moweagua, Illinois, on 2 March 1905, son of the late Thomas I. and Florence Reid (Myrick) Ahl. He attended Morton High School, Richmond, Indiana; received the degree of Bachelor of Arts from Earlhan College, Richmond, in 1925, and was awarded the degree of Doctor of Medicine from the Indiana University School of Medicine at Bloomington in 1929. On 4 June 1929, he was commissioned a Lieutenant (jg) in the Medical Corps of the US Navy, and subsequently advanced in rank, attaining that of Captain, to date from 1 August 1943.
Upon receiving his appointment in 1929, he was assigned to the US Naval Hospital, San Diego, California, to serve his period of internship. In September 1930 he joined USS New Mexico as junior Medical Officer, and in May 1931 transferred in a similar capacity to USS Arkansas. For five months, January-June 1933, he was Ward Medical Officer at the Naval Hospital, Mare Island, California, after which he had duty as District Surgeon with the Civilian Conservation Corps at Redding, California.
He was assigned as Ward Medical Officer, Eye, Ear, Nose and Throat, at the Naval Hospital, Brooklyn, New York, from October 1934 until September 1935, followed by instruction at the Naval Medical School, Washington, DC. In May 1936 he reported as Senior Medical Officer of USS Charleston, and in November 1938 was detached for duty as Ward Medical Officer at the Naval Hospital, Great Lakes, Illinois. He remained there until May 1939, after which he served as Medical Officer of the Naval Recruiting Station, Cleveland, Ohio. While at Cleveland, Ohio, he received post graduate instruction in Ophthalmology at Western Reserve University Hospital, and also served as an assistant instructor for medical students in the Eye Clinic.
From October 1940 until May 1941 he was Chief of the EENT Service at the Naval Hospital, Honolulu, Territory of Hawaii, and was serving as Senior Medical Officer on board USS Concord upon the United States' entry into World War II, 8 December 1941. In October 1942 he reported as Station Medical Officer at the Naval Training Station, Farragut, Idaho, and in July 1943 became Executive Officer at the Naval Hospital, Oceanside, California. He reported in December 1944 as Senior Medical Officer of USS Missouri, and while attached to that battleship, saw action during the FIFTH Fleet raids against Honshu and Nansei Shoto, the assault and occupation of Iwo Jima, the FIFTH and THIRD Fleet raids in support of operations at Okinawa Gunto and the THIRD Fleet operations against Japan.
He was on board the Missouri for the signing of the surrender documents on 2 September 1945.
Detached from the Missouri in October 1945, he returned to the United States for duty as Executive Officer at the Naval Hospital, Medford, Oregon. He was Chief of the Eye, Ear, Nose and Throat Department at the Naval Hospital, Norfolk, Virginia, from January 1946 to June 1947, after which he attended the basic course in ophthalmology at Portland, Maine. In September 1947 he reported as Chief of the Eye, Ear, Nose and Throat Department at the Naval Hospital, Portsmouth, Virginia, and in September 1950 transferred in a similar capacity, to the Naval Hospital, Oakland, California.
In January 1953 he became Executive Officer of the Naval Hospital, Charleston, South Carolina, where he remained until August 1955, when he was ordered to duty as Commanding Officer of the Naval Hospital, Jacksonville, Florida.
Captain Ahl had the American Defense Service Medal, Fleet Clasp; the American Campaign Medal; the Asiatic-Pacific Campaign Medal; the World War II Victory Medal; the Navy Occupation Service Medal, Asia Clasp; and the National Defense Service Medal.
Dr. Ahl was a Diplomate of the American Board of Ophthalmology; a Fellow of the American Academy of Ophthalmology and Otolaryngology; and the American College of Surgeons.