[2] The United States had entered World War I on 6 April 1917, and he arrived at the academy as a member of the Class of 1921 at a time when the school's student body and staff were growing rapidly to meet the need for naval officers in the expanding wartime navy.

[5] Ingersoll reported aboard the battleship USS North Dakota (BB-29) on 8 July 1920 to begin his first tour of duty as a naval officer.

[8] Promoted to lieutenant (junior grade) on 5 June 1923, he was serving aboard the destroyer USS Sicard (DD-346) in the United States Asiatic Fleet by the beginning of 1924.

During this period, U.S. Navy PBO Hudson patrol aircraft from Argentia sank the first two German submarines (U-boats) sunk by the United States Armed Forces during World War II.

In October 1943, he received the Legion of Merit for his tour aboard Card, the citation reading in part: ...During a period of intense anti-submarine activities in the North Atlantic, Captain Ingersoll was responsible for detailed supervision of convoy escort operations.

[27]On 10 April 1944[28] Ingersoll became the commanding officer of the light aircraft carrier USS Monterey (CVL-26), which operated in the Pacific Ocean in the United States Third and Fifth Fleets.

[5] He received the Navy Cross for his actions during the Formosa raids and the Battle of Leyte Gulf, the citation reading in part: ...for extraordinary heroism and distinguished service in the line of his profession as Commanding Officer of the Light Aircraft Carrier U.S.S.

When the MONTEREY came under heavy Japanese aerial attack while boldly penetrating the hazardous waters off Formosa on 13–14 October [1944], Captain Ingersoll fearlessly held his courage and, hurling the full fighting strength of his planes, despite terrific odds succeeded in blasting a number of hostile aircraft from the sky with no damage to his own vessel.

During the Battle for Leyte Gulf on 25–26 October 1944, he inflicted heavy damage and destruction upon capital ships of the Japanese fleet in a bitterly fought, decisive engagement.

Captain Ingersoll's inspiring leadership and the valiant devotion to duty of his command contributed in large measure to the outstanding success of these vital missions.

Urged to abandon ship by United States Third Fleet commander Admiral William F. Halsey Jr., Ingersoll exhibited determination to save Monterey in ignoring the order as he directed his crew – which included future U.S. U.S. President Gerald R. Ford – to extinguish the fire and displayed excellent seamanship in saving the ship.

[41] Ingersoll returned to sea as the commander, Carrier Division Four, then in June 1953 became chief of staff and aide to the Commander-in-Chief, United States Atlantic Fleet.

During his presidency, he oversaw the changeover of the college's wargaming from manual to computerized processes,[46][47] and on 13 November 1958, the Naval Electronic Warfare Simulator (NEWS) was commissioned in Sims Hall.