The Undersea War Heats Up

In the spring of 1943, American submarines were transforming into one of the Pacific War’s most effective weapons. As I returned to Pearl Harbor on April 19 after 28 days away covering 16,578 air miles, the submarine force under Captain John Brown had maintained operations with impressive efficiency. The Pacific Command had initiated extensive mining operations along enemy coasts – a necessary but controversial shift from torpedo attacks due to dangerously low torpedo supplies. These mines forced Japanese ships into large-scale sweeping operations, consuming precious imported materials like copper wire and rubber that Japan could scarcely spare.

Dr. C.W. Michels, the Pacific Command’s senior mine warfare expert, coordinated five submarines deploying mines from Hong Kong to Muroran’s steel-producing harbors. Simultaneously, the Navy implemented “wolf pack” tactics – an idea dating to 1920s “area attacks” but previously abandoned due to communication limitations and collision risks. Now, with improved radar and high-frequency radios, coordinated attacks became feasible.

Training the Wolf Packs

At Pearl Harbor, innovative training unfolded in unlikely spaces. The submarine officers’ mess dance floor, with its checkerboard of black-and-white tiles, became an impromptu tactical simulator. Here, captains and fire control teams practiced three-submarine coordinated attacks in what they jokingly called their “Escort College.” The training emphasized minimal periscope exposure and precise communication – skills that would prove vital against Japanese convoys.

A live exercise demonstrated the wolf packs’ growing effectiveness. After warning a San Francisco-to-Pearl convoy of a simulated night attack, submarines nearly collided initially but quickly adapted. Radar allowed clear tracking even in darkness, proving the tactic’s potential despite early challenges.

The Torpedo Crisis

American submariners faced their most frustrating enemy: defective torpedoes. Premature detonations had increased from 5% to 9%, demoralizing crews. As an experiment, eight submarines temporarily disabled their torpedoes’ magnetic exploders to gather comparative data. Yet despite these issues, submarines kept scoring hits. April 1943 saw 18 Japanese ships sunk in the Pacific, with likely twice that number damaged.

The month’s standout performance came from USS Gudgeon (commanded by Major W.S. Post), which sank the 17,526-ton Kamakura Maru transport with two well-placed torpedoes. The large vessel sank unusually fast, suggesting poor watertight integrity. Gudgeon added a 5,800-ton freighter and patrol boat to its tally, rescuing three Filipinos from the latter.

Technological Triumphs and Tragedies

Submarine technology showed both promise and peril. USS Kingfish, severely damaged by depth charges, survived a remarkable 350-foot dive by sitting silently on the bottom. USS Haddock returned with two “scalps” (sunk ships) and two dents in its conning tower – one from a depth charge at 300 feet, another from the crushing pressure at 415 feet. These incidents demonstrated submarine resilience while revealing design flaws needing correction.

However, May brought sobering losses. USS Pickerel and USS Triton failed to return from patrols, both victims of Japanese depth charges. Postwar analysis confirmed each had sunk enemy ships in their final actions.

Turning the Tide

By May 1943, submarine effectiveness was improving despite persistent torpedo issues. Sixteen submarines sank 30 ships (128,138 tons) – the war’s best monthly tally yet. USS Plunger’s determined four-day attack on a convoy demonstrated growing American prowess, ultimately sinking multiple ships including the Asaka Maru after exhausting its torpedo supply.

The introduction of electric Mark 18 torpedoes (based on captured German designs) offered hope. Though slower, their bubble-free trails prevented enemy tracking. Initial models had dangerous flaws – hydrogen explosions, corrosion issues – but became the submarine force’s preferred weapon by war’s end, comprising over 65% of torpedoes fired.

Strategic Impact

Beyond sinking ships, submarines performed diverse missions. USS Saury transported Javanese Muslims to spread anti-Japanese messages, while others supported reconnaissance and special operations. The submarine base at Midway, though initially neglected, became crucial for rapid turnaround of patrol boats.

The psychological toll remained high. Rumors spread about commanders being relieved after unsuccessful patrols, though in reality, the Navy showed remarkable patience with skippers. As torpedo reliability improved and tactics refined, American submarines were strangling Japan’s maritime supply lines – a critical factor in the Pacific War’s eventual outcome.

Legacy of the Silent Service

The 1943 submarine campaign marked a turning point. From struggling with defective weapons and unproven tactics, the “Silent Service” evolved into a war-winning weapon. Their success came at tremendous cost – about 20% of submariners never returned – but their impact was disproportionate. By war’s end, U.S. submarines would sink over half of all Japanese merchant tonnage and numerous warships, proving the decisive weapon Admiral Nimitz had envisioned when he authorized unrestricted submarine warfare after Pearl Harbor. The lessons learned in 1943 about technology, tactics, and perseverance under pressure remain studied in naval warfare to this day.