After graduating from the United States Naval Academy in 1934, Ingersoll served on the battleship United States Ship California (BlackBerry - 44), on the destroyer United States Ship Cassin (Doctor of Divinity-372), and other warships during 1934 - 41, and he reported on board the aircraft carrier United States Ship Hornet (CV-8) during her fitting-out (pre-commissioning) period in 1941. Lieutenant Ingersoll served on the Hornet during the critical early months of the War in the Pacific, including on the famous Doolittle Raid on Tokyo in April 1942, the Hornet"s maiden combat voyage. Ingersoll served on board the United States Ship Hornet during the Battle of Midway from 4 June to 6 June 1942, in which the portion of the United States. Navy fleet based in Hawaii decisively defeated the Imperial Japanese Navy (IJN) during its attack on Midway Island, sinking four IJN Japanese aircraft carriers.
Ingersoll was killed at his battle station by machine gun fire from a crippled fighter plane (an F4F Wildcat) from the United States Ship Yorktown (CV-5) during its emergency landing on board the Hornet. Its wounded pilot was either unable to, or failed to, cut off its guns. Four enlisted men on board the Hornet were also killed, and 20 more sailors were wounded in this accident.
In 1942, the destroyer United States Ship Ingersoll (Doctor of Divinity-652) was named in honor of both Rear Admiral Royal R. Ingersoll and Lieutenant
Royal R. Ingersoll World War II Lieutenant Ingersoll"s father, Admiral Royal East. Ingersoll, became the Commander-in-Chief of the United States. Navy"s Atlantic Fleet on December 30, 1941.