Topp's ninth war patrol on "U-552" went to the North Atlantic, west of Spain. Leaving Saint-Nazaire on 9 June, Topp sank five ships totalling before returning to port ten days later. Topp formed part of a strong wolf pack against Convoy HG 84. Topp engaged the convoy west-northwest of A Coruña. Topp achieved all his successes on this patrol against HG 84. On his tenth and last war patrol on "U-552", Topp sank two ships of and damaged two further of . Topp had left Saint-Nazaire on 4 July and returned from the North Atlantic on 13 August. Upon his return, he was awarded the Knight's Cross of the Iron Cross with Oak Leaves and Swords () on 17 August. He was the 17th member of the Wehrmacht to be so honored. That day, he also received a preferential promotion to "Korvettenkapitän" (Corvette Captain) and Dönitz presented him an honorary dagger of the "Kriegsmarine" with Diamonds.