“As the war continued, American tactics, detection gear and weaponry evolved to take the fight to Dönitz’s Wolf Packs.”
By Alan C. Carey
IT WAS NAZI GERMANY’S commander-in-chief of U-boats, Karl Dönitz, who was to preside over one of the Third Reich’s most ambitious strategies of the Second World War: to defeat the Allies by severing Britain’s trans-Atlantic shipping link with the Americas.
To achieve victory, Dönitz’s ordered his submarines to sink the maximum possible tonnage of enemy shipping per day, in an effort to neutralize Britain’s lifeline with the outside world. By destroying the enemy’s merchant fleet faster than Allied shipyards could replace the losses, Berlin believed it could force the United Kingdom to the peace table.
In the war’s first year, Dönitz’s submarines were limited in what they could accomplish due to the fleet’s relatively small size and the fact that Germany had no bases on the Atlantic. In 1939, the Third Reich’s only U-boat pens were on the Baltic and North seas. Dönitz’s subs would need to slip by the British Isles to reach the open ocean. All that changed in mid-1940, however, with the fall of France and establishment of submarine bases along the Bay of Biscay.
The new harbours allowed submarine operations to expand beyond European waters, out as far as the eastern shores of Canada and the United States, the Gulf of Mexico, the Caribbean and even South America. The Mediterranean would also now be within reach.
To counter the threat, the U.S. Navy waged a relentless campaign against Germany’s Unterseeboots – beginning with neutrality patrols and later through offensive operations. And as the war continued, American tactics, detection gear and weaponry evolved to take the fight to Dönitz’s Wolf Packs. Air power would play a critical role in that campaign
By the summer of 1943, U.S. sub-hunting patrol planes ranged as far north as Iceland, south to Brazil, and covered all points in between. America’s navy also established bases in French North Africa to cover the Mediterranean and even flew sorties from England over the Channel and the Bay of Biscay. Meanwhile, the formation of hunter-killer groups centred around escort carriers allowed aircraft to operate in areas far beyond the range of conventional land-based patrol planes.
In effect, U.S. naval aviation played a decisive role in the U-boat war, claiming as many as 80 of the 783 German vessels lost during the war. Italian and Vichy French submarines and at least one Japanese submersible fell prey to U.S. naval aircraft operating in the Atlantic.
American success in the air campaign against Hitler’s U-boat was a long time in coming. The U.S. Navy began operations against the Wolf Packs with few personnel, ships or aircraft suitable for the role. The widening of operations in the Pacific further strained America’s capability.
Naval aviation likewise could offer little at the onset of war, due to a shortage of air crews and adequate numbers of patrol aircraft.
Such problems were relatively short-lived, however, as Stateside aircraft manufacturers stepped up plane production.
By the end of the United States’ first year at war, the navy’s air arm was operating an impressive list of aircraft with squadrons conducting anti-submarine warfare (ASW) from bases strewn across the Atlantic. By 1943, escort carriers joined the hunt with operations sweeping large areas of the north and mid-Atlantic.
ASW technology and tactics had also evolved since the United States’ first campaign against U-boats during the First World War.
In 1918, enemy submarines were spotted by crews flying short-range patrol aircraft using mostly just binoculars. Attacks were carried out with free-fall bombs. Victories, which were few, were more a result of luck than skill.
By early 1942, the arsenal of detection equipment available to the Allies had expanded by leaps and bounds. The introduction of land- or ship-based, high-frequency direction finders (HF/HD) allowed for ground and air coordination. Using bearings pinpointed by radio detection, aircraft could be directed towards enemy targets with lethal effectiveness. Air-to-surface radar mounted aboard naval patrol planes also became instrumental in locating surfaced submarines far beyond visual range.
By the summer 1943, naval aircrews were also deploying acoustic sonobuoys to track U-boats by the cavitation of their screws, while magnetic anomaly detection (MAD) gear could identify a submerged submarine from the air.
The weaponry of patrol aircraft was also becoming deadlier. Early in the war, .30 and .50-caliber machine guns were used to suppress surfaced U-boats’ anti-aircraft defences; by the end of the war, homing torpedoes were the tool-of-choice.
Rockets mounted on planes like the F4F and TBF were also effective against surfaced submarines.
But of course, the depth charge (AN/Mk-17, AN/Mk44, and AN/Mk-47) was the most important weapon in the Allied anti-submarine arsenal.
These would later be joined by the Mk-24 Aerial Mine, known interchangeably as Zombie, Proctor, or Fido. An air-dropped torpedo with the ability to home in on the cavitation noise of a submarine’s screws, the weapon was developed during the fall of 1941 and was in use by March 1943.
While America’s surface fleet was engaging U-boats even before the United States’ official entry into the war, the first kill by a U.S. naval aircraft occurred on March 1, 1942. That’s when a plane from Navy Patrol Squadron 82 (VP-82) attacked and destroyed Korvettenkapitän Ernst Kröning’s U-656 off Newfoundland. Pilot Ensign William Tepuni spotted the vessel and dropped a pair of depth charges as the submarine was diving. A large oil slick appeared moments after detonation. Forty-five souls were lost. U-503 met a similar fate two weeks later at the hands of another aircraft of VP-82.
Mk-24 acoustic torpedoes took their toll on enemy subs, as well. On May 25, 1943, U-467 (Oberleutnant zur See Karl-Heniz Nagal commanding) became the first U-boat sunk by the weapon. It was dropped by a PBY Catalina from VP-84.
The first successful tracking of a U-boat through HF/DF and airborne radar from a U.S. land-based naval aircraft occurred when PBM-3C Mariner P-1 of VP-74 sank Type IXC U-158 (Kapitänleutnant Erwin Rostin commanding) west of Bermuda on June 30, 1943.
A joint effort by a MAD-equipped PBY Catalina – the gear’s first successful deployment – and British warships destroyed U-761 in the Mediterranean Sea on Feb. 12, 1944.
On May 22, 1943, aircraft operating in the mid-Atlantic from the USS Bogue became the first escort carrier planes to sink a U-boat. The target, U-569, was the first of nine submarines destroyed by pilots from the Bogue over the next 15-months.
TBF Avengers of VC-1 (Navy Composite Squadron One) based aboard USS Card successfully employed Mk-24 torpedoes sinking U-117 on August 3, 1943. TBF Avengers of VC-13 from USS Guadalcanal conducted the first successful FFAR (Forward Firing Aerial Rockets) attack against U-544 on Jan. 16, 1944; the vessel sank from a combination of depth charges and rockets.
Technological innovations, combined with increasing numbers of Allied ships and aircraft, ended the U-boat’s dominance, as the hunter became the hunted. The German High Command kept the mounting losses a closely-guarded secret, even withholding the information from its own submariners returning from patrol. Would such young men have freely joined the U-boat service between 1944 and 1945 had they known of the catastrophic losses being suffered?
By the 1944, serving on a U-boat was effectively a death sentence; it was American pilots flying naval aircraft who served many of those sentences.
ABOUT THE AUTHOR: Alan C. Carey is the author of Sighted Sub, Sank Same: The United States Navy’s Air Campaign against the U-Boat. His books have been published in the United States and U.K. while magazine articles have appeared in the United States, Australia and Brazil. Carey has served as a guest speaker at military reunions, aiding families in providing documentation and guiding individuals with collecting documentation on family members who served in the military, interviewed by national and international media, and has appeared on the History Channel.
