By mid-1942, the towering German battleship Tirpitz stood alone as the largest, most powerful warship in the world. Despite rarely venturing from her lair deep within the Norwegian fjords, her mere presence in the region forced the British Royal Navy to keep a large number of capital ships in home waters to watch over Allied convoy routes to the Soviet Union.
The fact that the menacing shadow of one ship could hold so many others virtually captive in the North Atlantic at a time when they were desperately needed elsewhere was an intolerable situation in the eyes of Britain’s Prime Minister, Winston Churchill. “The greatest single act to restore the balance of naval power would be the destruction or even crippling of the Tirpitz,” he wrote. “No other target is comparable to it.” His obsession with the massive dreadnought was the driving force behind numerous Royal Air Force and Royal Navy attempts to sink her, but all had met with failure.
The harsh reality was that inside Norwegian waters the Tirpitz enjoyed the protection of an ice-clad fortress bounded by sheer walls of solid rock and enhanced by German ingenuity. The natural defenses had been substantially bolstered by the deployment of countless artillery batteries and antiaircraft guns in the surrounding mountains while close-quarter protection for the 42,000-ton battleship was provided by layers of heavy antitorpedo nets that were closed around her like a second skin. Nothing had been left to chance, and within these all-encompassing defenses, the Germans confidently believed the “Lonely Queen of the North,” as the Tirpitz was known, was untouchable. To the Royal Navy looking on from afar, it was not an idle boast.
Churchill wanted action, but the British Admiralty could see no way to strike at its nemesis. Naval bombardment was impossible due to the configuration of the intervening land, the fjords were mostly beyond the range of land-based bombers, and a raid by conventional submarines would be suicidal.
The X-Craft Program
However, from within the deepening gloom that beset the Royal Navy, a ray of light emerged. For a number of years, Navy engineers had been working on the prototype for a 51-foot, 30-ton, four-man midget submarine specifically designed to attack naval targets in strongly defended anchorages. They had developed, in effect, a complete submarine in miniature, but in lieu of torpedoes, the midgets were fitted with two crescent-shaped detachable explosive charges fitted externally on either side of the pressure hull. These mines, each containing two tons of Amatex explosive, were to be planted on the seabed directly under the target ship then detonated with a variable time fuse.
It was deemed unlikely that the German command ever envisaged a raid by midget submarines or X-craft, as the British vessels were known, giving rise to optimism that at last an attack on the Tirpitzmight stand a fighting chance of success. It was a tantalizing prospect.
Winston Churchill, a renowned enthusiast of covert operations, had been greatly impressed by an earlier raid launched by Italian divers against British ships in Alexandria harbor and was eager for the X-craft to replicate a similar feat against the Tirpitz. His impatience to strike, however, was tempered by a Royal Navy that would not be rushed. While operational considerations dictated that these vessels would require many unique features, Navy experts were determined to develop the X-craft prototype along principles firmly grounded in reality and based on sound submarine practice. Within the halls of the Admiralty there was little enthusiasm for the unconventional, outlandish approach typical of the Special Operations branch.
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Even at this early stage of X-craft development, the sheer volume of pipes, dials, gauges, levers, and other vital equipment crammed inside the tiny hull left very little space for crew comfort. Navy planners recognized only that men possessing extraordinary self-control could cope with the claustrophobic conditions, and they sought volunteers “for special and hazardous duty” from among newly commissioned Royal Navy officers. The candidates, including many from Australia and South Africa, were not told what the mission entailed, but over the next few months, they were filtered through rigorous selection criteria. The physically unsuitable, the timid, or men with a “death or glory” outlook were steadily weeded out. Those who made the grade quickly found themselves undergoing intense training and theoretical courses on the X-craft.
Training and weapon development proceeded simultaneously, as further modifications, tests, and sea trials were conducted until the final construction design was approved. With the aid of civilian firms, the first six vessels, designated X-5 through X-10, rolled off the line to form the fledgling 12th Submarine Flotilla.
The Plan to Sink the Tirpitz
As the momentum of the operation gathered speed, bold theory predictably collided head-on with practical application. Before any attack could be launched, a number of significant roadblocks would need to be cleared, not the least of which involved getting the X-craft to Norway. Experts agreed that German patrols and air reconnaissance ruled out launching the vessels from a depot ship near the Norwegian coast, and a weeklong journey across the North Sea was considered beyond the endurance of the four-man crew. They would be completely exhausted before they ever reached the target. It was a vexing problem, but after much deliberation it was decided that the midgets would be towed to the operational area behind patrol submarines using 200-yard manila or nylon cables.
Even under tow, however, the 1,200-mile journey would still take eight days, so “passage crews” would be trained to ferry the craft to the target area. Then these men would be swapped with the “operational crews” who would make the voyage in the towing submarines.
These transit crews would play a vital, yet largely unsung role in the operation. Theirs would be an exacting, demanding duty in which they were to remain virtually submerged throughout the entire journey, only coming to the surface every six hours for 15 minutes to ventilate their hulls. It promised to be a voyage of incredible hardship, and few envied them.
Another critical factor in the planning was the timing of the raid. By early 1943, the Norwegian Battle Group of Tirpitz, the battlecruiser Scharnhorst, and the pocket battleship Lutzow had relocated to new berths within the small landlocked basin of Kaafjord, northern Norway. The German ships were now anchored five degrees north of the Arctic Circle where there was no darkness in summer and no light in winter.
Summer was unsuitable for a British attack because the X-craft needed the cover of darkness to recharge their batteries; winter deprived them of daylight to make visual contact with the target. The most favorable times for an attack occurred during the two occasions each year when daylight and darkness were equal, the equinoxes in March and late September. March was too soon, so the Admiralty settled on late September with the attack to go in on September 22. Navy planners had been swayed by intelligence reports from Norwegian agents indicating that on this date the Tirpitz’s 15-inch guns would be stripped and cleaned, and her sound detection equipment would be down for routine servicing.
In June 1943, specialized training for what came to be called Operation Source started in earnest when men and machines moved to the secret wartime base known as Port HHZ in Loch Cairnbawn, northern Scotland. Amid tight security, the Navy had designed a course that replicated the fjord up which the men would travel to attack the Tirpitz and her escorts, Scharnhorst and Lutzow. Now putting their new X-craft through trials, the men vying for selection carried out simulated attacks, rehearsed towing procedures behind larger submarines, and perfected techniques for cutting through antisubmarine nets. The men grew accustomed to the squalid, cramped interior of the vessels, but they never learned to enjoy it.
Throughout their arduous training, the strengths and weaknesses of the volunteers were constantly evaluated; everything they did and said during these interminable months played a role in determining who would go and who would be left behind. If the mission were to stand any chance of succeeding, the personnel conducting it would need to be the very best, both mentally and physically. The Navy recognized that a midget submarine would get the men to within striking distance of the Tirpitz, but it would take cold-blooded courage and fierce determination to breach the defenses and sink her.