Submarine pen

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Main article: Submarine base

A submarine pen is a bunker to protect submarines or U-boats from bombing.

[edit] Bombing of German U-boat Pens in World War II

German World War II U-boat pens in France included Saint-Nazaire, Lorient, La Rochelle and Toulon. In Norway, Trondheim was the site of a large pen. U-boat pens constructing the German Type XXI submarine were located at Hamburg (Blohm & Voss), Bremen (AG Weser), and Danzig (F. Schichau).

German World War II U-boat pens were designed to be bombproof,^{[citation needed]} and for several years, Allied bombing failed to destroy the bunkers itself^[clarify][1] (the area near the Lorient pen was "heavily damaged"). After the success of bouncing bombs against dams, Tallboy and Grand Slam bunker buster/earth quake bombs were developed and used to attack the bunkers.

Target	Date	Result
Kiel	July 23/24, 1944	In the first major raid on a German city for two months, 629 aircraft - 519 Lancasters, 100 Halifaxes, 10 Mosquitos - were dispatched in this first RAF raid since April 1943 and the heaviest RAF raid of the war. In a raid lasting only 25 minutes, all parts of Kiel were hit but the bombing was particularly heavy in the port areas and all of the important U-boat yards and naval facilities were hit. The presence of around 500 delayed-action bombs or unexploded duds caused severe problems for the rescue and repair services. There was no water for 3 days; trains and buses did not run for 8 days and there was no gas for cooking for 3 weeks.[2]
Brest	August 5, 1944	15 Avro Lancasters of No. 617 Squadron RAF attacked the Brest U-boat pens and scored 6 direct hits with Tallboy bombs penetrating the concrete roofs. 1 Lancaster was shot down by flak. Subsequent attempts to reinforce other sites with even thicker concrete diverted resources from other projects.[2]
Lorient, France	August 6, 1944	Flight Lieutenant Thomas Clifford Iveson dropped one Tallboy at the Keroman U-boat pen.[3]
Lorient, France	August 7, 1944	The Tallboy bombing mission to Lorient was scrubbed[3]
La Pallice	August 8, 1944	Flight Lieutenant Thomas Clifford Iveson dropped one Tallboy bomb.[3]
La Pallice & Bordeaux	August 11, 1944	53 Lancasters and 3 Mosquitos of No 5 Group attacked U-boat pens at Bordeaux and La Pallice with 2,000lb armour-piercing bombs, but the bombs did not penetrate the roofs. No aircraft lost.[2]
Brest, La Pallice, & Bordeaux	August 12, 1944	68 Lancasters of No 1 Group and 2 Mosquitos of No 5 Group attacked pens at Brest, La Pallice and Bordeaux without loss. A U-boat was believed to have been hit at La Pallice.[2]
Brest	August 13, 1944	28 Lancasters and 1 Mosquito of No 5 Group attacked the U-boat pens and shipping at Brest. Hits were claimed on the pens, on the hulk of an old French battleship, the Clémenceau, and on a medium-sized tanker. The object of the attacks on ships was to prevent the Germans using any of the large ships in Brest to block the harbour just before its capture by American troops. [2]
La Pallice & Bordeaux	August 16, 1944	25 Lancasters and 1 Mosquito of No 5 Group to attack the U-boat pens at La Pallice found the target was cloud-covered and only 3 aircraft bombed. No aircraft lost.[2]
La Pallice	August 17, 1944	Mission 559: A B-17 Flying Fortress dropped BATTY TV bombs on La Pallice.[4] One impacted 1 mile (1.6 km) short and the second about 1 mile to the right of the target.[5]
Ijmuiden	August 28, 1944	Flight Lieutenant Thomas Clifford Iveson dropped one Tallboy bomb.[3]
Heligoland	September 3, 1944	The US Navy controller flew the SAU-1 drone (B-17 42-63954)[6] into Duene Island by mistake.
Heligoland	September 11, 1944	During the first Castor mission of Operation Aphrodite, the pilot of B-17 42-30180 (Guzzlers) was killed when his parachute failed to open at bailout.[7]
Heligoland	October 15, 1944	Mission 678A:[4] B-17 42-30039 Liberty Belle[1] (differs from 42-30096 'Liberty Belle' lost due to accidental on-board fire and the Liberty Belle (B-17) 44-85734) and B-17 42-37743 of Operation Aphrodite attacked the Heligoland U-boat pens.[7]
Bergen	October 28/29, 1944	237 Lancasters and 7 Mosquitos of No 5 Group attack the U-boat pens at Bergen. The area was cloud-covered and the Master Bomber tried to bring the force down below 5,000ft but cloud was still encountered and he ordered the raid to be abandoned after only 47 Lancasters had bombed. 3 Lancasters lost.[2]
Heligoland	October 30, 1944	Mission 693A:[4] One Castor Operation Aphrodite drone (B-17 42-30066 MugWump) lost contact and went out of control and crashed near Trollhattan, Sweden. The other drone was B-17 42-3438.[7]
Ijmuiden	December 15, 1944	Flight Lieutenant Thomas Clifford Iveson dropped one Tallboy.[3]
Ijmuiden	December 30, 1944	13 Lancasters of No 617 Squadron set out to bomb the U-boat pens at Ijmuiden but the raid was abandoned because of bad weather.[2]
Ijmuiden	January 12, 1945	No 617 Squadron attacked the U-boat[3] pens with Tallboys, but smoke obscured the results.[2]
Bergen[3]	January 12, 1945	32 Lancasters and 1 de Havilland Mosquito of Nos 9 and 617 Squadrons attacked U-boat pens and shipping in Bergen harbour. 3 Lancasters of No 617 Squadron and 1 from No. 9 Squadron RAF were lost; the Germans told the local people that 11 bombers had been shot down. A local report says that 3 Tallboys penetrated the 3½-metre-thick roof of the pens and caused severe damage to workshops, offices and stores inside.[2]
Ijmuiden & Poortershaven	February 3, 1945	36 Lancasters attacked U-boat pens at Ijmuiden (No 9 Squadron) and Poortershaven (No 617 Squadron) with Tallboy bombs. Hits were claimed at both targets without loss.[2]
Ijmuiden	February 8, 1945	15 Lancasters of No 617 Squadron dropped Tallboys on the U-boat pens at Ijmuiden without loss.[2]
Oslo Fjord	February 23/24, 1945	73 Lancasters and 10 Mosquitos carried out an accurate attack on a possible U-boat base at Horten on the Oslo Fjord. 1 Lancaster was lost.[2]
Bremen (Farge)[8]	March 27, 1945	20 Lancasters of No. 617 Squadron RAF attacked the Valentin submarine pens,[9] a huge, nearly-ready structure with a concrete roof 23 ft thick. Two Grand Slam bombs penetrated two metres and detonated[9], which rendered the shelter unusable. No aircraft were lost.[2]
Hamburg	April 9, 1945	17 aircraft of No. 617 Squadron with Grand Slams and Tallboy bombs successfully attacked the U-boat shelters. No aircraft were lost.[2]
Kiel	April 9/10, 1944	591 Lancasters and 8 Mosquitos of Nos 1, 3 and 8 Groups to Kiel. 3 Lancasters lost. This was an accurate raid, made in good visibility on two aiming points in the harbour area. Photographic reconnaissance showed that the Deutsche Werke U-boat yard was severely damaged, the pocket battleship Admiral Scheer was hit and capsized, the Admiral Hipper and the Emden were badly damaged. The local diary says that all 3 shipyards in the port were hit and that the nearby residential areas were severely damaged.[2]
Kiel	April 13/14, 1944	377 Lancasters and 105 Halifaxes of Nos 3, 6 and 8 Groups to Kiel. 2 Lancasters lost. This raid was directed against the port area, with the U-boat yards as the main objective. Bomber Command rated this as 'a poor attack' with scattered bombing.[2]
Heligoland	April 18, 1945	969 aircraft - 617 Avro Lancasters, 332 Handley Page Halifaxes, 20 de Havilland Mosquitos of all groups - successfully used Tallboy bombs to attack the Naval base, airfield, & town into crater-pitted moonscapes. 3 Halifaxes were lost,[2] and the islands were evacuated the following night.

[edit] References and Note