At 1515 on 21 June 1940, a jubilant Adolf Hitler stepped from his Mercedes touring car into the forest clearing of Compiègne, near Paris. After a mere six weeks of mostly uninspired fighting, France—his most feared enemy—had been defeated. Seated in the same chair and in the same railway car from which a victorious Marshal Ferdinand Foch had dictated humiliating surrender terms to Germany on 11 November 1918, the 22-year wait for revenge was over. Germany would occupy more than half of the country, including the strategic Atlantic naval bases of Brest, Lorient, St. Nazaire, La Pallice, and Bordeaux. In signing away national sovereignty, France was forced to allow the Kriegsmarine to base its feared U-boat flotillas on the Bay of Biscay.
Before long, a daring, vastly intricate, and astonishingly successful construction project transformed the five Biscay ports into indestructible U-boat bunker bases. Six decades later, the enormous, monolithic structures still hulk over the town centers from which they were gouged—horrifying in their intent, incredible in their accomplishment, and still among the greatest construction feats of all time.
Drained from occupied Europe, concrete and steel measuring in the millions of tons sheltered the new pens. Under a punishing 24-hour-a-day regimen imposed by the German general contractor Organization Todt, hundreds of German, French, Belgian, and Dutch contractors designed and manufactured electrical equipment, high-speed pumps, mechanical systems, submersible caissons, overhead cranes, transformers, generators, and complete power stations. Steel mills, smelters, and smithies fabricated underground fuel lines, counterweighted armored double doors, steel trusses, lock gates, corrugated-steel coverings, dry-dock gantries, and railway tracks. Assembled on site were never-before-imagined or attempted marine tilting turntables. Gigantic positioning traversers would move 1,763-ton Type IXB U-boats from pierside to open pen in one hour. And after exhausting land-based resources, even the seabed was mined to suction sand for concrete.
Implausibly, while the shelters' deep foundations were exposed and vulnerable behind fragile cofferdams, construction continued at a fever pitch under the almost daily observation of British forces and went mostly unchallenged. As for beleaguered Britain, it was truly alone, outgunned, and outflanked in its own backyard. From Norway's North Cape to the Spanish frontier, the Greater Reich had become master of the continent and its seas.
Less than 48 hours after the French armistice, a long train left U-boat headquarters in Wilhelmshaven and continued through Paris without pause. Its destination: Lorient, on the remote and rocky Brittany coast. In addition to torpedoes, radios, navigation and optical instruments, spare parts, food, and drink, the train accommodated the small personal staff of 49-year-old Commander-in-Chief U-boats—newly promoted Vizeadmiral Karl Dönitz. The admiral's mission was to transform the Biscay ports into impregnable bastions, and expand the sea war of attrition deep into the Atlantic from bases now 450 miles nearer the dense shipping lanes of the Western Approaches.
In that mournful late June 1940, as France lay stricken under the Nazi jackboot, Dönitz headquartered his command in a requisitioned château at Kerneval on the Scorff River roadstead, within view of the developing bunker base. The first boat, the U-30 (commanded by Fritz-Julius Lemp, who had sunk the British liner Athenia on the war's first day), tied up at the Lorient piers only two days later. Some flotillas remained in Germany and Norway, but from Lemp's Lorient arrival until the Allied invasion of Normandy in 1944, almost every Atlantic U-boat had a Biscay homeport.
Traversing treacherous sea highways to deliverance or disaster, by mid-1940 the North Atlantic convoys already were in grave danger. Outbound from the United Kingdom, merchant shipping could rely on naval escorts only to 100 miles west of Ireland, while convoys eastbound from the United States and Canada were on their own a mere 400 miles from North America. With the French ports under German control, a vast uncontested mid-Atlantic gap—the "black hole"—became accessible to Biscay-based U-boats. The effect was immediate.
In the first full year of war, an average of only six U-boats at sea at any one time sank more than 1,000 merchant ships loaded to the gunwales with more than four million tons of armaments, tanks, trucks, planes, provisions, raw materials, aviation fuel, and oil. By mid-1940, the Royal Navy had only a two-month reserve of oil. Little more than a year later, in September 1941, a quarter of the entire British merchant fleet lay on the ocean floor. An agonized Sir Dudley Pound, the British First Sea Lord, put it starkly: "If we lose the war at sea we lose the war." As beleaguered Britain confronted defeat, Germany tasted victory and Atlantic Wall preparations were shunted to secondary status. Completion of the U-boat pens became the top priority.
With esteem bordering on worship, the submarine force regarded Admiral Dönitz as much more than commander-in-chief. Admired throughout the navy, the men had elevated the unemotional leader they called "the lion" to a higher rank of father figure, teacher, and master of their young lives. Like a good father, the admiral indulged his boys—affectionately calling them his "gray wolves"—with special chartered trains home and minimum one-month leaves, or generous liberty in "U-boat sailors' pastures"—requisitioned French seaside resorts. The U-boat pay schedule was almost double that of the other service branches, and with the often-compliant women in the Biscay ports, there was pleasure after the peril. "We are living like gods in France," went the saying. Until the war's last days, U-boat crews were given the best rations, the highest quality bread, meats, fruits and vegetables, and ample quantitites of good German wine and lager beer. Officers and men lived equally hard and fast. Why not? Most of them would pay soon enough with their lives.
As each U-boat returned after battle with white victory pennants fluttering like washing in the wind, shipyard workers and other crews cheered the gaunt, grimy sailors mustered on deck wearing salt-encrusted gray leather jackets, faces unshaven and reeking of diesel fuel. As a military brass band thumped, a bearded, white-capped young captain, only a few years older than his crew, inspected the steel-helmeted honor guard. Nurses in white tunics and girlfriends from town scattered fresh flowers. There was a swelling of pride and more than a little arrogance. Had the crews not earned it? After all, Lorient was then "the base of the aces." In 1942, the heyday of the U-boat's offensive in the Atlantic, a dozen Biscay U-boats each accounted for more than 100,000 tons sunk. No navy ever had nor ever would again achieve that.
From the château at Kerneval, Admiral Dönitz introduced the soon-to-be-dreaded Rudeltaktik or wolf pack strategy, a brilliant exploitation of flaws in the Allied convoy escorting system. From the secure Biscay pens, a mere handful of U-boats—averaging only eight at one time, and now with added range—changed the battle's focus by extending the war to the East Coast of the United States.
The offensive against U.S. shipping began with a captains' briefing in the château's operations "museum." As Admiral Dönitz waved the U-boats out to sea from the grassy terrace over the commo bunker, Paukenschlag ("Operation Drumbeat") began. Later, when the war turned against them, the crewmen would reminisce about the "American Turkey Shoot."
Beginning on 4 January 1942, only 27 days after Pearl Harbor, 12 1,120-ton, 253-foot Type IX boats launched a coordinated, two-phased attack. By the end of June, the order "torpedoes los" had sent nearly 400 merchants ships to the bottom, most flying the U.S. flag. The Americans were careless and conspicuous in their own waters, foolishly found again and again in periscope crosshairs. The tally was highest for coastal-running vessels steaming one behind the other like swaying elephants on parade, their lights undimmed, crews untrained, no radio silence, and their silouhettes displayed perfectly against the blazing lights of cities that had yet to be blacked out. From Hampton Roads to Miami Beach, local chambers of commerce seemed to be advertising directly to the U-boats. Even worse, most of the ships lost were tankers, and only six U-boats were sunk. Though a combination of aircraft, escorts, and new technologies eventually turned the tide in the Allies' favor, the basing of the U-boats on the French coast changed the strategic nature of the war and brought the Germans the closest they ever came to winning the war at sea.
Of all the cruel arts and sciences in the Nazi arsenal, only the Biscay bunker bases were built to last for at least the regime's promised thousand-year reign. Compare the construction requirements of only the Lorient bunker base with the accomplishment of another modern-day wonder, Hoover Dam. From 1931 to 1936, 5,000 men controlled the Colorado River and built a dam equivalent to a 65-story skyscraper. Still one of history's greatest engineering feats, the dam contained 4.4 million cubic feet of concrete poured over a 1,244-foot length and 726-foot height. That singular accomplishment almost was exceeded by just one of the five bases. In Lorient, beginning 2 February 1941, 15,000 mostly slave laborers and German overseers began three separate pen enclosures 2,000 feet in total length, 425 feet wide, and 63 feet high, topped further by a seven-section, 25-foot reinforced concrete roof--itself a daring work of extraordinary engineering skill. Finished in only 23 months, concrete mixers in the hundreds and trucks by the thousands poured concrete exceeding 3.4 million cubic feet. For comparison, Chicago's Sears Tower, for years the world's tallest building, would fail to reach the Lorient pens' total length by 600 feet. The Titanic twice over—with 400 feet to spare—could occupy the combined Lorient pens.
Construction raced ahead as the five Biscay shelters swallowed 14 million cubic feet of concrete and one million tons of steel. By mid-1942, the Allied Bomber Command had awakened fully to the threat the bases posed. It was too late; although construction was interrupted, it never stopped. The Germans recorded at least 300 air raids on Lorient alone by the U.S. Eighth Air Force and British Bomber Command. Not one mission succeeded in putting the pens out of commission.
Much more than fortified U-boat enclosures, the pens were more like complete naval bases under concrete. Feeding the unquenchable needs of repair and overhaul facilities, underground pipes delivered oil, gasoline, lubricants, fresh water, and seawater. All the necessities and many conveniences equivalent to a medium-sized town lay behind solid 11-foot-thick reinforced concrete external walls and three-foot-deep steel armored double blast doors. Extending hundreds of feet within the immense interiors were complete steam and electric generating stations, air-raid shelters, 1,000-man-capacity crew dormitories, cold storage and food lockers, mess facilities, and scores of drafting and engineering offices. Other spaces contained fire-fighting, repair, and first-aid stations, supply and storage rooms, kitchens, bakeries, and hospital and dental facilities. Separate bunkers housed electrical transformers, fuel tanks, and stand-by power generators. Dangerous or delicate stores such as torpedoes, ammunition, and optical instruments went to fortified bunkers in town.
A five-step system ingeniously moved a U-boat from pier to enclosed dry-dock pen in only one hour. In the final stage, with the U-boat secure in a cradle set on a trolley, a giant 32-wheel traverser—an electrically driven mobile platform—moved laterally over eight rails to stop opposite an empty pen for final placement inside. Each base had multiple dry docks, but the largest—Lorient—had 19 dry- docks in three separate pen enclosures, called Keroman I, II, and III. Sideways-moving traversers linked two of the three enclosures. Of 1,149 major wartime overhauls at the five bases (each lasting approximately one month), almost half were completed in Lorient. During the Battle of the Atlantic's most critical periods—even during merciless air raids—Lorient berthed up to 28 U-boats simultaneously. After the war, in grudging admiration, the U.S. Strategic Bombing Survey called Lorient "the world's greatest submarine base."
After years of relentless bombings, how could the bunker bases survive--and even be strengthened—without significant damage? One man had an answer that was echoed by many. First Lieutenant (later Captain) Edward J. Hennessy, stationed at Thurleigh in East Anglia, flew 25 missions as the command pilot of the B17F "Little Audrey." A Chicagoan and 1940 Notre Dame graduate, and only 23, Hennessy was on his third mission over St. Nazaire when flak took out an engine. "We had damage from [Focke-Wulfs] and [Messerschmitts] every mission. Our fighters didn't have the range, so in those early days we always flew without fighter escort," he said. "Everything was tried against the sub pens without results. One time we loaded 2,000-pound Navy 16-inch battleship shells fitted with tail fins, hoping to hit the ‘garage doors.' They bounced off just like the others. It convinced us that nothing was going to take out the pens, and we were right—nothing did."
With the most complete roof system of the five bases, the St. Nazaire pens received the least damage. If they saw anything at all from 25,000 feet, Allied flight crews discerned only a roof superstructure, the topmost of seven roof levels above the pens. To detonate bombs and direct the blast to an open six-and-a-half-foot-high explosion chamber below, German engineers designed the fangrost or "bomb trap" superstructure--inverted, concrete, U-shaped beams set on parallel slabs. An enclosed concrete layer under the explosion chamber (the third section) continued down to another solid section, then to a triangular interior void formed by tilting concrete U-beams against each other. Serving as a second bomb trap, the void also redistributed enormous weight loads to exterior walls. The combination of fangrosten, an explosion chamber, and the void redirected bomb impacts and contained penetrating explosions. Below the triangle-shaped void, additional concrete reinforcement encased a steel-trussed framework spanning each pen's eight-foot-thick dividing walls. A final corrugated steel layer, the only section viewed from the pens, served as the covering above the U-boats. In all, seven anomalous dense overlays up to 25-feet thick protected the U-boats.
After hundreds of raids only dimpled the pens, a new Allied weapon—the "Tallboy"—entered the scene. Sporting offset fins for bullet-like twisting, the 12,000-pound ballistic bomb was so heavy it could be dropped only from relatively low levels, thus negating much of its penetrating ability. In bases with incomplete fangrost defenses, some hits actually penetrated to the pen berths. But after hundreds of attempts, not one Tallboy pierced roofs with the complete seven-layer fangrost system. At war's end, the five bunker bases remained fully functional, but the five once-peaceful seaports and their surroundings were destroyed completely.
After the German surrender, the U.S. Strategic Bombing Survey counted 3,000 artillery pieces along the entire Atlantic Wall. Sited on land, flak ships, and flak towers, 300 heavy-caliber guns defended Lorient. Numerous Luftwaffe fighter bases and 40,000 Wehrmacht troops encircled the bunkers. Surrounding the pens, bristling from firing ports, casemates, flak towers and armored turrets, scores of 20-mm, 75-mm, 88-mm, 105-mm, and 128-mm guns awaited the enemy. No combat zone was protected more fiercely. But Festung Lorient withered on the vine, as the U.S. 66th Infantry and 4th Armored Divisions wisely skirted Lorient on the march to Germany.
When it was over, only two forsaken U-boats remained within the intact Lorient bunker base. One was scuttled, while the other—the still-seaworthy U-123—was reflagged as the French S-10 Blaison and sailed unremarkably from Lorient until 1959.
In 2,160 days of fearless and increasingly desperate combat, 28,000 of the once-proud German untersee force (a 70%-loss rate) would never again see the fatherland. Almost all went to the bottom with their boats. Their average age was 22.
In hundreds of heroic missions, many over the Biscay pens, the Eighth Air Force lost 30,000 men, a 10%-death rate—ten times higher than for U.S. ground forces. Almost 4,000 rest under Portland stone tablets in the American cemetery outside Cambridge, England. Their average age also was 22.
The unchanged, intact, and forgotten Lorient and St. Nazaire bunker bases will open to worldwide tourism sometime in 2000.
The Wolves' Elegant Lair
From a small desk in a sunny, windowed room with the harbor and bunker pens behind him, Admiral Karl Dönitz calculated his moves like a wily chessmaster. Unlike his Wehrmacht counterparts, Dönitz often changed U-boat strategy and tactics within hours, not days. Seven department heads—all U-boat veterans—examined overnight B-Dienst radio intercepts, daily U-boat summaries and positions, weather conditions, spy reports, and convoy and warship movements--indeed, a minute examination of every known variable and trend. With targets selected and patrol lines secured across likely convoy routes, orders went out: "attack and report sinkings."
From the château's kitchen, a narrow stone stairway descends to the basement through armored double doors to a three-section, 10,000-square-foot, wood-paneled, reinforced concrete bunker. The château's bunker was completed by Organization Todt in 1941, and remains little known to this day. A 200-man downstairs signals staff prepared "appreciations" for the upstairs operations officer's proposal to the admiral. Numerous one-by-three-foot partition openings between the low-ceilinged bunker's 14 rooms permitted incoming radio messages, decrypts, and intelligence reports to be distributed efficiently by the signals staff. Received or transmitted messages were encoded with Enigma or Geheimschreiber ("secret writer")—the two presumably impenetrable cipher machines used by the Germans throughout the war.
Essential to wolf pack tactics, torrents of two-way messages maintained contact but showed flagrant disregard for radio silence. U-boat command transmissions set operational areas, determined spare parts and torpedo status, arranged refueling, U-boat rendezvous, and organized personnel and supply transfers. Converted into diagrams, bar graphs, and charts, the ensuing reports augmented intricate letter and number-coded grid squares identifying every U-boat and all known enemy shipping around the world. Spiked like fever charts, elaborate wall graphics illustrated cumulative Allied losses, which by early 1942 neared 40 ships sunk for each U-boat lost. Writing in his war diary, Dönitz said, "the tonnage war is the U-boat's main task, probably their decisive contribution."
Like monks assembling for prayer, U-boat captains dutifully reported to the admiral after each war patrol. In a 10-by-12-foot, richly paneled, parquet-floored antechamber opposite the busy operations room, an assistant at his shoulder recording the exchange, Dönitz probed relentlessly. "Describe enemy tactics, strategy, disposition, technology, new weapons," he demanded. "Explain U-boat actions taken or opportunities missed." If a boat returned with torpedoes still in her racks, the reasons needed to be plausible. Like commanders everywhere, the admiral must have questioned why some captains were more successful than others.
The presumed operational advantages conferred by obsessive attention to detail did little good and much that was bad for U-boat fortunes. The Ultra codebreakers at Bletchley Park outside London methodically solved most messages within hours (see the author's "Secret at Bletchley Park," December 1997 Naval History, pages 34-38), often before Dönitz had returned to the château from afternoon walks with his dog Wolf, an Alsatian. There were other factors, but by mid-1943 the wolf packs had been defeated, and U-boat command relocated to Berlin.
One of only three undamaged buildings in a town of 46,000 and now completely rebuilt, the château and signals bunker survived intact. The château, now the port admiral's residence, is closed to visitors. Scattered throughout Lorient, 12 concrete supply bunkers, appearing like hideous abscesses on a smooth surface, also remain.
On 9 May 1945, the U.S. 66th Infantry Division used the château's captured transmitters to inform a long-afflicted populace that they were free again.
Jerome M. O'Connor