The Type 201 is 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 not been tested extensively enough and showed up to be problematic in service with the Bundesmarine: Microscopic cracks in the pressure hull forced the cancellation of 9 of the 12 ordered submarines and the early retirement of the three built boats. They were replaced by the very similar Type 205 submarines, that were constructed with normal steel.

List of boats

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Pennant number	Name	Shipyard	laid down	Launched	com- missioned	decom- missioned	fate
S180	U1	HDW		1962	March 20 1962	1967	rebuilt to Type 205A standards
S181	U2	HDW		1962	May 3 1962	July 1963	rebuilt to Type 205A standards
S182	U3	HDW		1962	June 20 1964
S183	U4	HDW		1962	not completed

U3 was loaned to the Royal Norwegian Navy and served under the name Kobben from 1962 to 1964 before being commissioned in the German Navy.

References

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• Taucher.net (in German)

Submarine classes | Submarines of Germany