Saint-Nazaire and targeted the shipping routes in the North Atlantic, south of Iceland. On this patrol, the BdU credited Topp with the sinking of three ships and one escort totaling . The patrol ended on 6 May, again in Saint-Nazaire. In reality, Topp sank three ships totaling , and damaged one ship of which was then sunk by (Adalbert Schnee). The third ship sunk during Topp's second patrol in command of U-552, was the troopship S.S. Nerissa (5,583 GRT, 207 casualties and 84 survivors) on 30 April 1941 about 140 nautical miles west of the North Channel. This sinking resulted in the third-largest loss of life for a ship sunk by U-boats in the approaches to the British Isles during the Second World War. On 25 May, Topp took U-552 on its third war patrol. The next day, U-552 returned to Saint-Nazaire before heading for North Channel on 3 June. The BdU assumed that Topp sank three ships of and he was awarded the Knight's Cross of the Iron Cross () on 20 June 1941. This patrol ended on 2 July in Saint-Nazaire. Later analysis revealed that the true tonnage sunk accumulated to . One of the ships was the Norfolk. The vessel carried mail and steel plates among 4,000 tons of general cargo. Captain Frederick Lougheed and 69 men were saved; one man was lost. Korvettenkapitän Harro Schacht was Topp's commander in training on U-552s fourth war patrol. The patrol, which began on 18 August and ended on 26 August in Saint-Nazaire, resulted in the sinking of one ship of . This ship had previously been damaged by (Reinhard Suhren). Following this patrol, Topp was promoted to Kapitänleutnant (lieutenant commander) on 1 September 1941. The fifth war patrol took U-552 into the North Atlantic, patrolling southeast of Greenland. Topp left Saint-Nazaire on 4 September and sank three ships of . U-552 returned to Saint-Nazaire on 5 October. Reuben James and Second Happy time The next patrol began on 25 October and ended on 26 November 1941 in Saint-Nazaire. This was also Koitschka's last war patrol as first watch officer on U-552. On U-552s sixth war patrol into the North Atlantic, east of Grand Banks of Newfoundland, Topp sank the destroyer on 31 October 1941, the first United States Navy warship to be lost in World War II while it escorted Convoy HX 156. The torpedo struck a forward magazine,