The Type 201 was Germany's first class of military submarines built after World War II. They were built out of amagnetic steel to counter the threat of magnetic naval mines, but the material had been insufficiently tested and proved to be problematic in service with the Bundesmarine. Microscopic cracks in the pressure hull forced the cancellation of nine of the twelve ordered submarines and the early retirement of the three completed boats. They were replaced by the very similar Type 205 submarines, that were constructed with normal steel. Responsible for the design and construction was the Ingenieurkontor Lübeck (IKL) headed by Ulrich Gabler.