Four Type XXI boats were assigned to the USSR by the Potsdam Agreement; these were U-3515, U-2529, U-3035, and U-3041, which were commissioned into the Soviet Navy as B-27, B-28, B-29, and B-30 (later B-100) respectively.
Empat U-boat Tipe XXI diberikan kepada Uni Soviet sesuai dengan Perjanjian Potsdam; ini adalah U-3515, U-2529, U-3035, dan U-3041, yang ditugaskan dalam Angkatan Laut Uni Soviet masing-masing sebagai B-27, B-28, B-29, dan B-30 (nantinya B-100).