In some ways similar to his fellow honoree, Howard Gilmore, Cromwell consciously chose to sacrifice his own life to safeguard the lives of others, in a combat action which took place in November 1943.

As a senior officer, Cromwell was completely familiar with the plans for the upcoming Battle of Tarawa, Operation Galvanic,[3] and knew a lot more about ULTRA[4] – and its source – than anyone else on Sculpin.

[1] While attacking a Japanese convoy on November 19, 1943, Sculpin was forced to the surface, fatally damaged in a gun battle and abandoned by her surviving crew members.

Captain Cromwell, who knew secret details of the impending operation to capture the Gilbert Islands, deliberately remained on board as she sank.

However, while coming up, the broken depth gauge stuck at 125 feet, confusing the diving officer, and causing the boat to broach the surface in full view of Yamagumo, which was still patrolling the area.

Yamagumo's first salvo hit Sculpin's conning tower, killing the entire bridge watch team, including Connaway and his executive and gunnery officers.

With his personal knowledge of both ULTRA and GALVANIC, he realized immediately that to abandon ship and become a prisoner of the Japanese would create a serious danger of compromising these vital secrets to the enemy under the influence of drugs or torture.

[1] On the evening of December 3, 1943, 240 miles (390 km) southeast of Yokosuka – with some help from ULTRA – USS Sailfish (SS-192) sank Chuyo, and only one of the Sculpin prisoners on board survived.

[1] When the story of John Cromwell's heroic sacrifice was revealed in the accounts of the Sculpin survivors, COMSUBPAC VADM Charles Lockwood nominated him for the Medal of Honor.

Undertaking this patrol prior to the launching of our first large-scale offensive in the Pacific, Captain Cromwell, alone of the entire Task Group, possessed secret intelligence information of our submarine strategy and tactics, scheduled Fleet movements and specific attack plans.

Constantly vigilant and precise in carrying out his secret orders, he moved his underseas flotilla inexorably forward despite savage opposition and established a line of submarines to southeastward of the main Japanese stronghold at Truk.

Cool and undaunted as the submarine, rocked and battered by Japanese depth-charges, sustained terrific battle damage and sank to an excessive depth, he authorized the Sculpin to surface and engage the enemy in a gun-fight, thereby providing an opportunity for the crew to abandon ship.

Determined to sacrifice himself rather than risk capture and subsequent danger of revealing plans under Japanese torture or use of drugs, he stoically remained aboard the mortally wounded vessel as she plunged to her death.