The Hunt For I-16: How One Submarine Hunt Changed the Course of World War II

The U.S. Navy destroyer escort USS Spangenberg (DE-223) underway following her conversion to a radar picket destroyer escort. She was converted at the New York Naval Shipyard between June and September 1945.
February 14, 2020 Topic: History Region: Asia Blog Brand: The Buzz Tags: Imperial JapanWorld War IIPacific TheaterAnti-Submarine WarfareSaipan

The Hunt For I-16: How One Submarine Hunt Changed the Course of World War II

The last remaining Japanese surface fleet was relying on those submarines.

Admiral Soemu Toyoda needed answers. The newly appointed commander in chief of Japan’s Combined Fleet, Toyoda found himself facing several unpleasant facts. By May 1944, Allied naval and air strength in the Pacific Ocean was growing at an alarming rate. Already, fast-moving enemy forces had advanced far across northern New Guinea and into the Admiralties and through the Marshall Islands in the Central Pacific.

Toyoda could not yet determine whether the next American thrust would head north into the Marianas or continue west toward Palau and the Philippines. The six carriers, 10 battleships, and 40 other warships of his First Mobile Fleet could crush an enemy advance, but those vessels carried only enough fuel for one decisive sea campaign. Before sending Japan’s last remaining surface force into battle, Toyoda required hard evidence of American naval activity and intentions.

Much had changed since the heady days of 1941 and early 1942. Japanese long-range patrol aircraft, once able to roam far into Allied territory, could now only rarely penetrate the enemy’s air defense umbrella. Radio interception, so useful during the war’s first months, was rendered virtually useless by advanced American communications security procedures. That left submarines as Toyoda’s sole reliable means of reconnaissance.

Unfortunately, Japan’s largest, most capable fleet subs—the oceangoing I-class boats—were increasingly being pressed into service as transports hauling food and supplies to Imperial Japanese Army garrisons marooned by leapfrogging Allied forces. Scouting duties would have to be performed by the smaller Ro-class submersibles of Rear Admiral Noboru Owada’s Submarine Squadron Seven. These vessels were designed for coastal patrol, however, and lacked the surface radar systems Owada deemed so necessary for conducting reconnaissance missions.

What their crews did not lack was courage. Each Ro-class boat then anchored at Saipan in the Marianas held between 40 and 60 sailors, the cream of the Imperial Japanese Navy undersea force. Combat veterans all, these well-trained seamen posed a substantial threat to any Allied vessel caught in their periscope sights.

Yet Owada’s orders were to locate and report enemy warships not sink them. He directed his boats to picket a 200-mile track between New Guinea and the Caroline Islands labeled the NA Line. Should they spot an Allied armada steaming toward the Philippines, these scouts were sure to radio back with positive confirmation. Armed with this intelligence, Admiral Toyoda could then order his Combined Fleet into the climactic battle he believed would win victory for Japan.

On May 15, 1944, the seven Ro-class boats of Submarine Squadron Seven departed Saipan to take up stations along the NA Line. Their 650-mile voyage would take six days and was tracked closely both by Owada’s staff on Saipan and Combined Fleet headquarters in Japan.

The progress of Squadron Seven was followed by another group of naval officers, listening from a heavily guarded facility at the American naval base at Pearl Harbor, Hawaii. These men belonged to Fleet Radio Unit-Pacific (FRUPac), the top-secret signal intelligence center responsible for collecting and decoding all enemy radio communications intercepted by the U.S. Navy. Already FRUPac had helped win a stunning American victory at Midway, not to mention its role in Operation Vengeance, the ambush of Admiral Isoroku Yamamoto by U.S. Army Air Forces Lockheed P-38 Lightning fighters in 1943. This brilliant team of mathematicians, puzzle solvers, Japanese linguists, and electronics experts was about to change history once again.

A routine radio transmission, made on May 13, 1944, set in motion what would become one of the most epic battles in the annals of antisubmarine warfare. This short, encrypted message came from Lt. Cmdr. Yoshitaka Takeuchi, captain of the fleet sub I-16.  Takeuchi’s report, plucked from the airwaves by American technicians, advised Admiral Owada that his vessel was due to arrive with food and supplies for the bypassed garrison at Buin on the southwest tip of the island of Bougainville on May 20.

FRUPac analysts deciphered enough of Takeuchi’s dispatch to estimate his course and time of arrival at Buin. This information quickly made its way to Admiral William F. “Bull” Halsey’s Third Fleet headquarters, also at Pearl Harbor, for action. Halsey had to move fast, though, since intelligence such as this was extremely perishable. Countless factors from weather to mechanical breakdowns to unpredictable sea conditions might put I-16 miles from where the Americans thought it was. And just because FRUPac knew the whereabouts of an enemy sub did not mean the U.S. Navy could get hunter-killer teams there quickly enough to find and sink it.

Fortunately for the Allies, a small group of destroyer escorts (DEs), purpose-built to attack submarines, was then awaiting orders at Purvis Bay off Florida Island in the lower Solomons. The group, designated Escort Division 39, consisted of USS England (DE-635), USS George (DE-697), and USS Raby (DE-698), all newly commissioned Buckley-class vessels on their first war cruise. Kept busy thus far with routine convoy escort duties, few sailors aboard these three DEs had yet seen combat.

A series of events would rapidly transform them into seasoned veterans. On May 18, a communiqué from Third Fleet arrived directing Escort Division 39 to intercept a “Japanese sub believed heading to supply beleaguered forces at Buin.” After posting its estimated location, the electrifying message concluded: “He is believed to be approaching this point from the north and should arrive in that area by about 1400 [hours] 20 May. Good hunting.”

Each of the three DEs in Escort Division 39 measured 306 feet in length with a beam of 36 feet. Fully combat loaded, a Buckley-class destroyer escort displaced 1,740 tons. Two General Electric turbo-electric engines drove the vessel to a top speed of 24 knots, while maximum cruising range exceeded 5,000 miles. A ship’s company typically included 15 officers and 198 enlisted men.

A suite of electronic sensors assisted the crew in its mission of locating enemy targets. SL search radar helped find surface vessels, while SA “bedspring” radar identified possible aerial threats. But the DE’s primary detection system was QSL-1 sonar, which sent a pulse of high-intensity sound called a “ping” into the water. Echoes reflected off such solid objects as a submarine returned to the ship, where trained sound operators could then determine the contact’s range and bearing.

The destroyer escort also packed a lethal punch. Apart from 20mm Oerlikon and quad-mounted 1.1-inch antiaircraft cannons, each Buckley-class DE came equipped with three Mk 22 3-inch/50-caliber deck guns—two forward and one aft. Three 21-inch torpedoes in a triple tube launcher mounted atop the superstructure deck were intended for surface vessels, while a battery of depth charge projectors on the ship’s fantail could devastate plunging submarines with a string of “ashcans” each containing up to 600 pounds of high-explosive filler.

Just entering service in the Pacific that spring was a new and deadly weapon, the Mk 10 “Hedgehog” forward-firing spigot mortar. The DEs of Escort Division 39 all carried this British-designed projector, which fired a salvo of two dozen 24-pound contact-fused charges intended to fall in a circular pattern up to 270 yards ahead of the ship. Hedgehog rounds could be aimed to fall slightly right or left of center line and would only explode if they struck a submarine. By 1944, Japanese submarine captains had learned how to evade blindly dropped depth charges; Hedgehog-equipped destroyer escorts could now track a target on sonar throughout their attack and thus greatly increase the chance of a precision kill.

Sub hunting was a complicated, intricate task that required every officer, NCO, and bluejacket—from soundmen to Hedgehog gunners to the engine room gang—to work together as a team. Even the newest hands in Escort Division 39 knew their only chance to defeat the foe was through relentless training, and aboard one of those DEs training had become an obsession.

Since its commissioning in December 1943, the USS England, named for Ensign John Charles England, killed at Pearl Harbor, had earned the reputation of being a “taut ship.” Her crewmen devoted themselves to achieving excellence in equipment maintenance, ship handling and, above all, proficiency with the vessel’s weapons systems. They knew theirs was a kill-or-be-killed profession; coming in second against a Japanese submarine meant violent death on the lonely ocean.

Leading the England’s company to excellence was an unlikely taskmaster. Lieutenant John A. Williamson, a 26-year-old from Birmingham, Alabama, served as the ship’s executive officer (XO). Taking a reserve officer’s commission in 1940, Williamson soon found himself aboard the destroyer USS Livermore in the North Atlantic. Although the United States was then technically not at war, fully armed American warships on the “Neutrality Patrol” regularly shepherded convoys to and from Great Britain during the height of the U-boat peril. During his nine months of escort work, Williamson often witnessed firsthand the horrific toll that German subs were taking on Allied merchantmen.

Lieutenant Williamson next served as an instructor at the Subchaser School in Miami, where he helped train the Navy’s next generation of sonar operators. He then skippered a wooden-hulled patrol craft along the East Coast before receiving orders to join England for duty in Pacific waters. As XO, Williamson brought to his new ship a remarkable combination of battle experience, technical knowledge, and passion for excellence.