The Undersea Battlefield Emerges

By early 1943, the Pacific submarine war had entered a dangerous new phase. Japanese antisubmarine warfare tactics grew increasingly sophisticated, forcing American submarine commanders to adapt or perish. The once-permissive hunting grounds near Japan’s home islands now bristled with patrol boats, aircraft, and minefields – all learning from painful experience. This escalation came at tremendous cost to both sides, as evidenced by the disappearance of boats like USS Scamp (SS-277) in the Yellow Sea, likely claimed by one of Japan’s extensive minefields despite having sunk four enemy ships earlier in her patrol.

The strategic situation demanded innovation. That autumn, Admiral Charles Lockwood’s Pacific Fleet Submarine Force established the Submarine Operations Research Group (SORG) under Dr. Rinehart. This analytical team, working with IBM punch-card machines, revolutionized submarine tactics by statistically evaluating everything from torpedo spread patterns to evasion techniques. Their monthly bulletins became required reading for every submarine captain.

Turning Points in the Depths

March 1944 marked both triumph and tragedy. USS Sand Lance (SS-381), patrolling the frigid Kuril Islands “Polar Route,” sank the Japanese light cruiser Tatsuta in a daring night attack – one of three ships destroyed during a patrol that earned the Presidential Unit Citation. Yet this success was tempered by losses like USS Grayback (SS-208), one of the war’s most successful submarines. Japanese records later revealed a carrier plane had crashed directly into Grayback, detonating her torpedoes after she’d sunk 14 enemy vessels.

The introduction of electric Mark 18 torpedoes addressed the notorious failures of earlier magnetic exploders, though crews complained about battery fumes. Meanwhile, Japanese destroyers – now prioritized as targets – began disappearing at an alarming rate, crippling Japan’s convoy system. By May 1944, American submarines had sunk 55 merchant ships totaling 236,882 tons, plus six warships – surpassing previous monthly records.

Life and Death Beneath the Waves

Submarine warfare created surreal juxtapositions. The crew of USS Tunny (SS-282) rescued 22 downed aviators near Truk while under shore battery fire, discovering that Japanese gunners wouldn’t reveal their positions by firing at submarines when American planes were overhead. This led to innovative air-submarine rescue coordination that saved hundreds of pilots.

Yet “friendly fire” remained a constant threat. USS Seahorse (SS-304) narrowly avoided destruction when a B-24 Liberator bombed her, highlighting the perils of operating near Allied air operations. Submarine crews developed dark humor about these “trigger-happy” aviators, even as they risked their lives to rescue downed fliers.

Technological Arms Race

The underwater war spurred rapid innovation. American submarines experimented with new deception devices to evade sonar, while Japan introduced terrifying oxygen-powered torpedoes with twice the range of Allied models. Radar-equipped Japanese destroyers forced submarines to remain submerged longer, as USS Rock (SS-274) discovered when a 4.7-inch shell destroyed her periscope and radar mast during a nighttime chase.

The Mark 18 electric torpedo’s quiet running allowed closer approaches, though its hydrogen emissions sometimes forced crews to wear gas masks. Meanwhile, forward bases like Midway’s new submarine dock and the floating drydocks at Majuro Atoll kept boats operational despite punishing war damage.

Legacy of the Silent Service

By mid-1944, American submarines had achieved what prewar theorists only dreamed – they were strangling Japan’s maritime supply lines. The sinking of tankers cut Japan’s oil imports by 75%, while the destruction of merchant shipping halved the empire’s industrial capacity. Submarines accounted for 55% of all Japanese merchant losses, despite comprising just 2% of the U.S. Navy’s personnel.

The human cost was staggering – about 3,500 American submariners died, representing the highest casualty rate of any U.S. armed service. Yet their sacrifice was disproportionate to their impact. Submarine operations:
– Sank over 1,000 Japanese merchant ships (5+ million tons)
– Destroyed 214 warships including 8 aircraft carriers
– Rescued 504 downed aviators
– Provided critical reconnaissance for major operations

The submarine campaign demonstrated how a relatively small force, properly employed with technological superiority and aggressive tactics, could alter the course of a global war. Lessons about undersea warfare, joint operations, and strategic interdiction learned in these icy Pacific depths continue influencing naval doctrine to this day.