The True Story of the Only Underwater Submarine Battle Ever
The Hunt for Red October dramatized for the public one of the tensest forms of warfare imaginable: combat between submarines submerged deep under the ocean’s surface, the nerve-wracked crews scouring the fathomless depths for their adversary’s acoustic signature using hydrophones.
However, while hunting undersea enemies is one of the primary jobs of modern attack submarines, only one undersea sub engagement has ever taken place, under decidedly unique circumstances.
This is not to say that submarines have not sunk other submarines. Indeed, the first such kill occurred in World War I, when U-27 sank the British E3. Dozens other such engagements occurred in the two world wars. However, in all but one case, the victims were surfaced, not underwater.
This was foremost because the submarines of the era needed to spend most of their time on the surface to run their air-breathing diesel engines; they could only remain underwater for hours at a time with the power they could store on batteries, moving at roughly one-third their surface speed. Therefore, submerged action was reserved for ambushing enemy ships and evading attackers.
There were additional problems intrinsic to having one submarine hunt another underwater in an era that predated advanced sensors and guided torpedoes: how could submerged subs detect each other’s position? During World War II, submarines came to make greater use of hydrophones as well as active sonar; however, the latter models could only plot out a submarine’s location on a two-dimensional plane, not reveal its depth.
Furthermore, the torpedoes of the time were designed to float up to near the surface of the water to strike the keel of enemy ships. Although the “tin fish” could be reprogrammed to an extent, it was not standard to adjust for depth, and guessing the azimuth of an enemy submarine with the limited targeting information available posed an immense challenge.
U-864’s Secret Mission
On February 5, 1945, the U-Boat U-864 slipped from its quay in Bergen as it departed on a secret mission known portentously as Operation Caesar.
U-864’s compartments were filled with key technology and resources that Nazi Germany planned on transferring to Japan. These included schematics and components for Jumo 004 turbojets to aid in the development of a Japanese jet fighter, and even two engineers from the aviation manufacturer Messerschmitt. There were also guidance components for V-2 ballistic missiles and two Japanese technical experts. U-864 also carried more than sixty-seven tons of liquid mercury, carried in 1,857 steel flasks. The mercury had been purchased but not entirely delivered from Italy in 1942, and was a key material for manufacturing explosive primers.
Capt. Ralf-Reimar Wolfram’s mission was to sail the long-range submarine north around Norway, then across the Arctic Circle past Soviet territory to deliver the goods. Germany was only months away from falling, but Berlin hoped that the technology and materials would allow Japan to stay longer in the fight and divert Allied combat power.
U-864 was a Type IXD2 “cruiser submarine,” and at 87.5 meters long was larger than the more common Type VII U-Boat. It was designed for long-range transoceanic patrols, and the -D2 model in particular was even bigger to accommodate enlarged cargo compartments. Before departing, U-864 had been modified with a piece of technology then unique to Germany—a snorkeling mast, allowing the submarine to sip air from the surface while shallowly submerged.
Despite this formidable advantage, Wolfram’s mission proved ill-omened from the start. U-864 initially set off from Kiel on December 5, 1944, but ran aground while transiting through the Kiel canal. Wolfram decided to have the ship undergo repairs in Bergen, Norway. But in Bergen, its armored pen was hit with twelve-thousand-pound Tall Boy bombs dropped by British Lancaster bombers on January 12, 1945, causing even more damage.
Unfortunately for Wolfram, the United Kingdom had long ago cracked the Enigma code, which German U-Boats used to communicate with the Naval headquarters. By February, the British Navy had decoded messages relating U-864’s mission, and decided to set a trap.
HMS Venturer, the first of the new V-class submarines, received orders from the Royal Navy Submarine Command to hunt down and destroy U-864 off the island of Fedje, Norway. The smaller, shorter-range British submarine carried only eight torpedoes to U-864’s twenty-two, but it was nearly 50 percent faster underwater, at ten miles per hour.
Venturer arrived at its station on February 6. Its skipper, twenty-five-year-old Lt. James S. Launders, was a decorated submarine commander, who in addition to sinking twelve Axis surface ships, had dispatched the surfaced submarine U-711 in November 1944.
Though he disposed of an ASDIC active-sonar system that offered greater detection range by emitting sound waves into the ocean, which could be tracked when they pinged off submerged ships, Launders elected to rely on shorter-range hydrophones. This was because the ping from ASDIC could be heard by adversaries from even further away.