German submarine U-735 was a Type VIIC U-boat

U-boat

U-boat is the anglicized version of the German word U-Boot , itself an abbreviation of Unterseeboot , and refers to military submarines operated by Germany, particularly in World War I and World War II...

 built for the German

Nazi Germany

Nazi Germany , also known as the Third Reich , but officially called German Reich from 1933 to 1943 and Greater German Reich from 26 June 1943 onward, is the name commonly used to refer to the state of Germany from 1933 to 1945, when it was a totalitarian dictatorship ruled by...

 Kriegsmarine

Kriegsmarine

The Kriegsmarine was the name of the German Navy during the Nazi regime . It superseded the Kaiserliche Marine of World War I and the post-war Reichsmarine. The Kriegsmarine was one of three official branches of the Wehrmacht, the unified armed forces of Nazi Germany.The Kriegsmarine grew rapidly...

 for service during World War II

World War II

World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

. She served as a training boat preparing U-boat

U-boat

U-boat is the anglicized version of the German word U-Boot , itself an abbreviation of Unterseeboot , and refers to military submarines operated by Germany, particularly in World War I and World War II...

 crews for service in the Atlantic Ocean

Atlantic Ocean

The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...

. Her home base was Horten

Horten

is a town and municipality in Vestfold county, Norway—located along the Oslofjord. The administrative centre of the municipality is the town of Horten. The municipality also includes the villages of Borre, Åsgårdstrand, Skoppum, and Nykirke....

 in Norway

Norway

Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...

, from which she operated on short coastal patrols, practicing in fjords and channels for submarine warfare. A Type VIIC U-boat

German Type VII submarine

Type VII U-boats were the most common type of German World War II U-boat. The Type VII was based on earlier German submarine designs going back to the World War I Type UB III, designed through the Dutch dummy company Ingenieurskantoor voor Scheepsbouw den Haag which was set up by Germany after...

, U-735 was very useful for preparing sailors and officers for service in modern boats, as opposed to the new models usually used in training.

Commissioned at Christmas 1942 in Danzig after an exceptionally long building period, U-735 was given to Kptlt. Hans-Joachim Börner, who remained in command of the boat right up to her destruction exactly two years later, when he was killed on board his ship. Dispatched to Norway, Börner soon became an expert on the Norwegian seaways, and was able to train a large number of sailors on his practice missions from Horten.

On the 28 December 1944, RAF Bomber Command

RAF Bomber Command

RAF Bomber Command controlled the RAF's bomber forces from 1936 to 1968. During World War II the command destroyed a significant proportion of Nazi Germany's industries and many German cities, and in the 1960s stood at the peak of its postwar military power with the V bombers and a supplemental...

 sought to eradicate the menace of submarines sailing from Norwegian bases, and launched a major raid on Horten. U-735 was anchored in the naval harbour at Horten. When the air raid alarm came at 21.30, U-735 eventually succeeded in leaving the harbour, having had trouble starting her diesels. At 23.30 NE of Horten she caught the full force of a bomb, sinking just outside the harbour, south of Mølen Island, with 26 men killed and ten missing, including her captain. Only one crew member survived, plus ten crew members who were on leave in Horten. She was the only U-boat to be lost in the attack. The wreck was rediscovered by a Royal Norwegian Navy

Royal Norwegian Navy

The Royal Norwegian Navy is the branch of the Norwegian Defence Force responsible for naval operations. , the RNoN consists of approximately 3,700 personnel and 70 vessels, including 5 heavy frigates, 6 submarines, 14 patrol boats, 4 minesweepers, 4 minehunters, 1 mine detection vessel, 4 support...

 sub-sea surveillance ship, Tyr

HNoMS Tyr (N50)

HNoMS Tyr is a mine control vessel used for underwater search and recovery by the Royal Norwegian Navy.-History:Tyr was built at Voldnes Skipsverft in 1981 and was used as an offshore standby-ship in the North Sea under the name MS Sandby Master...

 in 1999. A high-resolution SAS

Synthetic aperture sonar

Synthetic aperture sonar is a form of sonar in which sophisticated post-processing of sonar data are used in ways closely analogous to synthetic aperture radar. Synthetic aperture sonars combine a number of acoustic pings to form an image with much higher resolution than conventional sonars,...

 image of the wreck made the cover of Sea Technology Magazine in June 2006 http://www.km.kongsberg.com/ks/web/nokbg0239.nsf/AllWeb/357F5BDF94329B0BC12571B6003200E5?OpenDocument. Two other ships were also sunk in the air attack: MT Holmengraa and Nordvard.