Guide
In the first years of the Second World War these submarines were used by Germany against British shipping in the North Sea; the first German naval success of the war came on its opening day off the Shetlands, when U-23, under one of the best-known German commanders, Otto Kretschmer, sank a British ship.
When Germany invaded Russia in 1941, Hitler decided to go after Soviet shipping in the Black Sea. Türkiye was neutral, so the straits were closed to German submarines. The answer was to take the boats apart. They were dismantled at Kiel in the north, brought by canal down to the Elbe, taken up that river to Dresden, loaded in pieces onto lorries and driven to Ingolstadt, put into the Danube there, and carried down to Constanţa in Romania. Six submarines made that journey of 3,300 kilometres, and from 27 October 1942 to 25 August 1944 they sank dozens of Russian ships. Three of them — U-9, U-18 and U-24 — were sunk in turn by the Russian navy.
When the Russians bombed Constanţa, the three that were left had nowhere to go. Hitler offered to sell U-20, U-23 and U-19 to Türkiye; İsmet İnönü refused an offer that could have counted as grounds for a declaration of war. Romania changed sides in August 1944 and declared war on Germany, which left the boats trapped in the Black Sea, and the Germans ordered them scuttled in open water.
One of them, U-20, was sunk by her own crew off Karasu in Sakarya. The wreck lies 2.5 kilometres from shore, with the conning tower at 18 metres and the bottom at 23. The world learned where she was in 2008, through a report in the Sunday Telegraph.