What were the Most Daring Missions of World War 2’s X-class Miniature Submarines?

During the Second World War a remarkable but often overlooked group of submarines played a crucial role in various operations, including the preparation for the D-Day invasion. These submarines, known as X-Craft, were small, specially designed vessels tasked with daring missions that often carried immense risk. Terry Bailey explains.

An X-Craft 25 in Scotland during World War 2.

The theatre of the Second World War, where naval supremacy often dictated the outcome of battles required innovation that became the key to success. Among the many remarkable developments of the era were the X-craft miniature submarines which stood out for the audacity, effectiveness and bravery of the crews who manned these vessels. The small but mighty vessels played a crucial role in some of the war's most daring and important missions, proving that size was no obstacle to bravery or impact.

The genesis of the X-Craft can trace its pedigree back to the CSS H. L. Hunley, the small Confederate States of America submarine that played a small part in the American Civil War. The Hunley’s mission profile, like the British X-craft of the Second World War was to close with the enemy vessel and deliver an explosive device next to or near the hull of the target vessel then retired from the area.

In the Second World War, the Allied forces faced the daunting task of neutralizing the formidable German battleship Tirpitz. Anchored in the remote fjords of Norway, the Tirpitz posed a significant threat to Allied convoys and naval operations in the North Atlantic. Traditional methods of attack, such as aerial bombing, had proven ineffective against the ship's heavily fortified defenses on the vessel and in the water including surrounding hills.

In response to this challenge, British naval engineers embarked on a daring experiment: the development of miniature submarines capable of infiltrating enemy harbors that could deliver a devastating blow to high-value targets. The result was the X-Craft, a revolutionary vessel measuring just 51 feet in length manned by a crew of four.

Operation Source

The X-Craft's first major mission came in September 1943, with Operation Source—the audacious plan to attack the Tirpitz in its heavily defended anchorage at Altenfjord, Norway.

Although a larger number of X-craft were assigned to Operation Source, however, only six eventually took part the mission, due to a number of unforeseen problems. Each craft was tasked with navigating treacherous waters and evading enemy patrols to reach their target after slipping from the mother submarine that towed the X-craft across the North Sea.

The journey itself was a testament to the courage and skill of the X-Craft crews, who endured cramped conditions and the constant threat of detection as they navigated through hostile waters. Despite facing numerous challenges, including mechanical failures and adverse weather conditions, two X-Craft, named X6 and X7, successfully reached their target and deposited their side charges under the Tirpitz, there is some evidence that indicates that X5 also managed laid their charges.

Although the attack failed to sink the battleship outright, it dealt a significant blow to the ship’s operational capabilities, forcing the Germans to withdraw the Tirpitz from active duty for repairs, providing the Allies precious time. The success of Operation Source demonstrated the potential of the X-Craft as a strategic weapon and paved the way for future missions.

Operation Guidance

Encouraged by the relative success of Operation Source, the X-Craft were subsequently deployed on a series of daring missions throughout the remainder of the war, including Operation Guidance.

In April 1944, Submarines X20 up-to and including X25 were dispatched to Bergen, Norway, as part of Operation Guidance. X24, under the command of a brave crew, attacked the Laksevåg floating dock. Originally, X22 was intended for this mission. However, tragically, it had been accidentally rammed during training and sunk, resulting in the loss of all hands.

Undeterred, X24 proceeded with the mission, although the charges were initially placed under the merchant vessel Bärenfels, causing its sinking, the dock itself sustained only minor damage. Determined to succeed, X24 repeated the operation in September, this time successfully sinking the dock.

Operation Postage able

Additionally, the X-Craft submarines were instrumental in the preparatory work for Operation Overlord, the Allied invasion of Normandy. One notable operation, Postage Able, involved X20, commanded by Lieutenant KR Hudspeth.

Spending four days off the French coast, X20 conducted periscope reconnaissance of the shoreline and echo-soundings during the day. Each night, two divers would swim ashore to survey the landing beaches, collecting samples for analysis.

Despite challenges such as fatigue and adverse weather conditions, the operation provided vital intelligence for the upcoming invasion. Lieutenant Hudspeth's leadership during this mission earned him a bar to his Distinguished Service Cross.

Operation Gambit

As part of Operation Gambit, X20 and X23, each manned by a crew of five, acted as navigational beacons to guide the D-Day invasion fleet to the correct beaches. Equipped with radio beacons and echo sounders, these submarines played a crucial role in directing Canadian and British ships to suitable positions on Sword and Juno beaches. The use of oxygen bottles enabled the crews to remain submerged for extended periods, contributing significantly to the success of the operation.

XE class submarines and Far East operations

In August 1945, the new improved XE class miniature submarines were deployed in a daring attack on Japanese warships within Singapore harbor. The mission was meticulously planned, with XE3 assigned to attack the heavy cruiser Takao, while XE1 targeting the heavy cruiser Myōkō.

XE3's journey was fraught with challenges, navigating through the Straits of Johor and evading harbor defenses. It took a total of 11 hours to reach the target area, with an additional 2 hours spent locating the camouflaged Takao. Despite the constant threat of detection by Japanese,  XE3 successfully reached the Takao, deploying limpet mines and dropping two side charges. The withdrawal was executed flawlessly, and XE3 safely returned to HMS Stygian, its towing submarine.

Meanwhile, XE1 encountered delays caused by Japanese patrol craft. Realizing that reaching Myōkō before the explosives laid by XE3 detonated was impossible, the captain made the strategic decision to target the already attacked Takao. Like XE3, XE1 successfully returned to its towing submarine, HMS Spark.

The impact of the attack was profound, the Takao, already in a damaged state, sustained severe damage and was rendered unfit for further use. For their extraordinary bravery and skill, the commanders and crews of both XE1 and XE3 were honored with prestigious awards. Lieutenant Ian Edward Fraser RNR and Leading Seaman James Joseph Magennis of XE3 were awarded the Victoria Cross (VC), the highest military decoration for valor.

Sub-Lieutenant William James Lanyon Smith, RNZNVR, received the Distinguished Service Order (DSO) for his role in commanding XE3. Engine Room Artificer Third Class Charles Alfred Reed, who operated the vessel's controls, was recognized with the Conspicuous Gallantry Medal (CGM).

In recognition of their contributions, Lieutenant John Elliott Smart RNVR and Sub-Lieutenant Harold Edwin Harper, RNVR, commanding officer and crew of XE1 respectively, were awarded the DSO and the Distinguished Service Cross (DSC).

Additionally, ERA Fourth Class Henry James Fishleigh, Leading Seaman Walter Henry Arthur Pomeroy, ERA Fourth Class Albert Nairn, Acting Leading Stoker Jack Gordan Robinson, and Able Seaman Ernest Raymond Dee were all honored for their roles in bringing the midget submarines to the point of attack, receiving various commendations and mentions in dispatches.

Legacy

The X-Craft missions during World War II may have been overshadowed by larger naval engagements, but their impact was profound. These small submarines played a vital role in disrupting enemy operations and weakening Axis forces.

The impact on the outcome of the Second World War is often underestimated, yet should not be dismissed, these diminutive submarines played a crucial role in neutralizing some of the most formidable naval threats of the era, demonstrating the effectiveness of unconventional warfare tactics in an increasingly complex battlefield environment.

Moreover, the legacy of the X-Craft extends far beyond their wartime exploits. The technological innovations pioneered in the development of these vessels laid the groundwork for future advancements in submarine design and underwater warfare.

The lessons learned from their operations continue to form military strategy and tactics to this day, serving as a testament to the enduring legacy of innovation and ingenuity in times of conflict. Moreover, their daring exploits served as an inspiration for today’s generation of naval special forces.

Therefore, it should be clear that the X-Craft miniature submarines represent a remarkable chapter in the history naval warfare. From their humble origins to Second World War experimental prototypes and their pivotal role in some of the most daring missions of the Second World War, these small but mighty vessels exemplify the courage, tenacity, and ingenuity of the men who manned them. Their story serves as a powerful reminder of the indomitable spirit of those who dare to defy the odds in the pursuit of victory.

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Japanese Anti-Submarine Warfare in World War 2: A Little Bit of Technology, a Little Bit of Luck

The U.S. submarine campaign in the Pacific during World War II is well known. However, less is known about the Japanese anti-submarine force that faced the U.S. submarines during the war. Daniel Boustead tells us about the Japanese campaign here.

U.S. submarine ace Richard H. O’Kane (right) being awarded the Medal of Honor by US President Harry S. Truman (left) in March 1946.

During World War II, the Japanese had important wins against the Allies. These wins were attributable to some well-developed technology, weapons, and tactics. The Japanese were also helped along  by several American blunders. The Japanese anti-submarine force was more effective than previously thought.

The Imperial Japanese Navy’s anti-submarine forces killed or captured two out three of the top three American Submarine Aces during World War II. The Japanese patrol craft  P-34 captured top American submarine ace Richard H. O’Kane between October 24th and  October 25th, 1944, when O’Kane’s sub-USS Tang was sunk by a circular run of its own torpedoes(1). O’Kane was the top U.S. Sub Ace with 27 ships sunk(11).  He would end up at the Ofuna P.O.W. Camp and the Omori P.O.W. camp in Japan for the rest of the war(12).

The Japanese also killed Number 3 American Sub Ace Dudley “Mush” Morton on October 11th, 1943 after Japanese airplanes sunk Morton’s Sub U.S.S. Wahoo. A total of over 60 depth charges and 40  bombs were expended against the sub at the  Le Perouse Strait(13). Dudley “Mush” Morton had sunk 19 Japanese Ships(14).

The Japanese anti-submarine campaign was beginning to have  a negative effect on the American submarine crewmen’s morale. For example, U.S.S. Harder Exec Tim Lynch said of his skipper Sam Dealey “Sam was showing unmistakable signs, of strain,”, (15). Lynch continued,  “He was becoming quite casual about Japanese anti-submarine measures. “Once, on the previous patrol, I found Sam in a sort of state of mild shock, unable to make a decision” (15).

Technology and tactics

By contrast the Allies  were only able to capture or kill  one out of three  of Nazi’s Germany Top U-Boat Aces during World War II. The British captured Otto Kretschmer on March 17th, 1941, after the British Destroyer HMS Walker brought Kretschmer’s boat U-99 to the surface after a long depth charge attack(2). Kretschmer was the Third Reich Top Scoring Ace with 47 ships sunk. He sent 274,418 tons of shipping to the bottom(3).

A total of 52 out of 288 U.S. subs that were commissioned were lost by the end of war. By September 2nd, 1945, the  loss rate was 18.06%(17). The Japanese sunk 41 out of 52 lost U.S. subs while they were on war patrol or due to enemy action. The other 11 were lost by various other causes.

The Japanese success can be attributed to technology and tactics. First, Japan’s radio direction finder network was very well developed(18). The Japanese were able to intercept almost all U.S. radio transmissions, except for very low or very high frequency calls. Thus, the Japanese could fix the position of a submarine transmitting on the surface within an area of about 100 square miles. This provided a means of keeping tabs on the U.S. subs in various areas, the number on patrol, and the general distribution in the Pacific. Japanese underwater listening gear was also excellent and echo ranging destroyers were always a threat to U.S. Subs. In the fall of 1943, the Japanese High Command organized the Grand Escort Fleet, along with an air escort squadron specifically designed to protect convoys against submarines.

By 1944, the Japanese radio detection system was growing more effective each month. Japanese Radio detection system was so successful it could intercept communications between subs in an American wolf pack. In addition, Japanese anti-submarine forces  were now equipped with electronic devices that could sense U.S. radar beams coming their way and could therefore detect American boats in the vicinity. The effect of Japanese electronic devices forced O’ Kane to keep his radar searches to a minimum and then only in short bursts(16). This development compromised O ‘Kane’s stealth.

Lastly, by early 1944, the Japanese had depth charges with an explosive charge of 1,000 lbs.  These weapons  could be set to explode at depth exceeding 600 feet (17). In 1944, they  were using new airborne radar in their night searches of U.S. subs. U.S. Subs were often subjected to night attacks by the Japanese while they recharged their batteries on the surface. Japanese planes carried standard bombs that were modified for use as an anti-submarine warfare weapon. Small planes were loaded with 150-pound bombs and larger aircraft dropped 625- pound bombs. The bombs were equipped with delayed-action fuses , which were set to explode at predetermined depth (16).

By 1944, the Japanese also began to organize anti-submarine air squadrons. The Japanese  around the same time , were putting up extensive anti-submarine minefields. These were planted in the hundreds in many areas where a U.S. submarine would be operating. The Japanese mined these areas all the time. This made it very difficult for the Americans to locate the mines. During much of the war many submarines were lost trying to locate Japanese minefields. By losing a submarine, it was the only reliable way for them to locate a Japanese minefield (16).

American mistakes

Beyond the technology and tactics, the Japanese campaign was helped along by two important American mistakes. First, the Bureau of Ordnance made a fatal mistake right before the war. They did not test fire the Mark VI magnetic exploder, which was used on the warhead section of Mark XIV steam driven torpedo (4).The decision was made out of secrecy and as a cost cutting measure. The Bureau of Ordnance claimed that their Mark VI magnetic exploder would only need one to shot to work. In actuality, U.S. submarines would fire six shots directly at the target, and it would still not work. Instead, torpedoes, weighted down by the magnetic exploder would either run too deep, explode prematurely (because of the intense magnetic field of the target), or fail to explode if they reached the target. The magnetic exploder was at fault for the first two short comings, while faulty contact exploder pins were responsible for the last problem. Consequently, American submarines would pursue daring attacks, only to see their torpedo wakes bubble under a target or prematurely detonate, giving away their position (5). This problem was so bad that not until October 1943, over 21 months after the start of hostilities, could American submariners put to sea and know that their torpedoes would actually work (6).

Even after this point,  there was still cases where there  were fatal torpedo faults that would cost lives. American submarine torpedoes would sadly sometimes do a dreaded a circular run where they would turn back and hit their submarine instead of hitting the target. This was fatally demonstrated between October 24th and October 25th 1944 , when a circular of run of torpedoes sunk U.S.S. Tang commanded by top U.S submarine ace O’Kane (7). This incident was exploited by the Japanese Anti-Submarine forces who picked up O’Kane and his crew (8). According to what he told his Japanese captors, the Destroyer U.S.S. Pruitt and his first Submarine the U.S.S. Argonaut were equipped with equipment to prevent circular runs (9). However early in the war,  for unknown reasons, the Bureau of Ordnance  had done away with anti-circular run devices aboard American Submarines and American  Destroyers. It was during O’Kane’s interrogation with his Japanese captors, that he stated his sub U.S.S. Tang was not the first victim of this fatal design flaw. Had the torpedoes been functioning properly the U.S. submarine force would have sunk more Japanese ships.

The second major mistake for the Americans occurred when an intelligence leak seriously compromised the secrecy of the U.S. submarine force. Congressmen Andrew Jackson May, a 68-year-old member of the House Military Affairs Committee, returned from a junket to the Pacific in the summer of 1943 and held a press conference (10). In that press conference, “He pointed out that the  Japanese claims of sinking U.S. subs were overstated, because their depth charges were set to go off too shallow. U.S. subs could avoid them by diving deep, perhaps deeper than the Japanese thought them capable” (10). The newspaper reports of this catastrophic blunder reached Japan and its Navy reset their depth charges accordingly. The Commander of U.S. sub forces Charles A. Lockwood was enraged by this congressional leak. Privately, Admiral Lockwood blamed Congressmen May’s bombast for the loss of U.S. submarines and lives (10). An incensed Lockwood wrote to a colleague: “I heard Congressmen May say the depth charges are not set deep enough. He would be pleased to know (they) set them deeper now.” (10) Later Lockwood wrote, “I consider that indiscretion cost us ten submarines and 800 officers and men”(10). How deeply a U.S. Submarine could dive was a closely held secret prior to this incident.

Conclusion

The Japanese anti-submarine campaign had important successes owing to strong radio direction technology. They were also assisted by great weapons, tactics, and other technologies. However, they were significantly aided by U.S foibles. Ultimately, the end of the war was brought about with the atomic bomb attacks and the Soviet Intervention in the Pacific War. The Japanese surrender cannot be attributed to the American submarine campaign.

What do you think of Japanese anti-submarine warfare in World War 2? Let us know below.

Now, you can read World War II history from Daniel: “Did World War Two Japanese Kamikaze Attacks have more Impact than Nazi V-2 Rockets?” here, “Japanese attacks on the USA in World War II” here, and “Was the Italian Military in World War 2 Really that Bad?” here.

Bibliography

Gruner, William P. U.S. Pacific Submarines in World War II. San Francisco Maritime National Park Association-2010. https://archive.hnsa.org/doc/sbinpacific.htm.

Holwitt, Joel Ira. “Execute Against Japan”: The U.S. Decision to Conduct Unrestricted Submarine Warfare. College Station: Texas. Texas A& M University Press-William-Ford Military History Series. 2009.

Keith, Don. Undersea Warrior: The World War II Story of “Mush” Morton and the USS Wahoo. United States of America. Caliber Press. 2011.

Paterson, Lawrence. Otto Kretschmer: The Life of the Third Reich’s Highest Scoring U-Boat Commander. Annapolis: Maryland. Naval Institute Press.  2018.

Tuohy, William. The Bravest Man: Richard O’Kane and the Amazing Submarine Adventures of the USS Tang. New York: New York. Presidio Press. 2006.

References

1 Tuohy, William. The Bravest Man: Richard O’Kane and the Amazing Submarine Adventures of the USS Tang. New York: New York. Presidio Press. 2006. 315-318 and  334.

2 Paterson, Lawrence. Otto Kretschmer: The Life of the Third Reich’s Highest Scoring U-Boat Commander. Annapolis: Maryland. Naval Institute Press.  2018. 194-204.

3 Paterson, Lawrence. Otto Kretschmer: The Life of the Third Reich’s Highest Scoring U-Boat Commander. Annapolis: Maryland. Naval Institute Press.  2018. 257.

4 Holwitt, Joel Ira. “Execute Against Japan”: The U.S. Decision to Conduct Unrestricted Submarine Warfare. College Station: Texas. Texas A& M University Press-William-Ford Military History Series. 2009. 162.

5 Holwitt, Joel Ira. “Execute Against Japan”: The U.S. Decision to Conduct Unrestricted Submarine Warfare. College Station: Texas. Texas A& M University Press-William-Ford Military History Series. 2009. 162-163.

6 Holwitt, Joel Ira. “Execute Against Japan”: The U.S. Decision to Conduct Unrestricted Submarine Warfare. College Station: Texas. Texas A& M University Press-William-Ford Military History Series. 2009. 163.

7 Tuohy, William. The Bravest Man: Richard O’Kane and the Amazing Submarine Adventures of the USS Tang. New York: New York. Presidio Press. 2006. 315-318.

8 Tuohy, William. The Bravest Man: Richard O’Kane and the Amazing Submarine Adventures of the USS Tang. New York: New York. Presidio Press. 2006. 334.

9 Tuohy, William. The Bravest Man: Richard O’Kane and the Amazing Submarine Adventures of the USS Tang. New York: New York. Presidio Press. 2006. 338.

10 Tuohy, William. The Bravest Man: Richard O’Kane and the Amazing Submarine Adventures of the USS Tang. New York: New York. Presidio Press. 2006. 164-165.

11 Tuohy, William. The Bravest Man: Richard O’Kane and the Amazing Submarine Adventures of the USS Tang. New York: New York. Presidio Press. 2006. 393

12 Tuohy, William. The Bravest Man: Richard O’Kane and the Amazing Submarine Adventures of the USS Tang. New York: New York. Presidio Press. 2006. 354 and 389.

13 Keith, Don. Undersea Warrior: The World War II Story of “Mush” Morton and the USS Wahoo. United States of America. Caliber Press. 2011. 263-268

14 Keith, Don. Undersea Warrior: The World War II Story of “Mush” Morton and the USS Wahoo. United States of America. Caliber Press. 2011. 312.

15 Tuohy, William. The Bravest Man: Richard O’Kane and the Amazing Submarine Adventures of the USS Tang. New York: New York. Presidio Press. 2006. 299

16 Tuohy, William. The Bravest Man: Richard O’Kane and the Amazing Submarine Adventures of the USS Tang. New York: New York. Presidio Press. 2006. 243-244.

17 Gruner, William P. U.S. Pacific Submarines in World War II. San Francisco Maritime National Park Association-2010. https://archive.hnsa.org/doc/sbinpacific.htm.

18 Tuohy, William. The Bravest Man: Richard O’Kane and the Amazing Submarine Adventures of the USS Tang. New York: New York. Presidio Press. 2006. 163-164.