the Iron Cross 2nd Class () in January 1940. On 1 May 1940, he was transferred to the 1st U-boat Flotilla. Command of U-57 After eight war patrols under the command of Kapitänleutnant Claus Korth, command of of the 1st U-boat Flotilla was passed to Topp on 5 June 1940. Topp's fifth war patrol began in Kiel on 11 July 1940 and was destined for the North Atlantic, into the North Channel, and the Minch. Because the Gruppenhorchgerät, a hydrophone array, was experiencing technical difficulties, Topp took U-57 to port for repairs. U-57 arrived in Bergen on 15 July, departed again that day only to return to Bergen on 20 July. Two days later, U-57 was able to begin her patrol. The Befehlshaber der U-Boote (BdU—supreme commander of the U-boat arm) credited Topp with the sinking three ships of of shipping. On 7 August, U-57 arrived in Lorient, France. On 14 August 1940, U-57 departed from Lorient on her 10th war patrol. Again, Topp led U-57 into the North Atlantic, the North Channel, and the Hebrides. On this patrol, Topp sank three ships of , and damaged another ship of . On 3 September 1940, U-57 collided with the Norwegian vessel Rona near the lock at Brunsbüttel and sank. Following the loss of U-57 — the boat was later raised and used for training purposes — Topp was awarded Iron Cross 1st Class () and initially remained with 1st U-boat Flotilla. On 4 November, he was sent to Blohm & Voss, the shipbuilding works in Hamburg, for construction training of , a Type VIIC U-boat. Transfer to U-552 On 4 December 1940, Topp took command of U-552 and commissioned the U-boat into the 7th U-boat Flotilla. Following sea trials and training, Topp, with Leutnant zur See Siegfried Koitschka as his second watch officer, took U-552 on its first war patrol on 13 February 1941. The patrol, which was destined for the North Atlantic west of Ireland, began in Kiel. That day, they headed for Brunsbüttel, where they stayed one day. The following day, U-552 made a stopover at Cuxhaven before leaving for Heligoland on 15 February. After three days at Heligoland, Topp took the boat into the North Atlantic. U-552s first patrol ended in Saint-Nazaire, France on 16 March 1941. On this patrol, Topp sank two ships of . The second patrol on U-552 began on 7 April 1941 from