The proposed alternative is to order more U-class boats before war begins, once the first three have demonstrated the design. Henderson's notes are cited in support of a January 1939 order, followed by another twelve boats in September. The actual September 1939 batch is criticized as too little, with a further ten boats following in March 1940 and more batches in August 1940 and July 1941. Keeping these small batches resembles prewar financial practice despite the wartime demand. First World War experience had already shown that submarine losses would require replacements. Northern European coastal work and Baltic access also justified small boats even before a Mediterranean commitment was certain. Their size and speed allowed them to work through the Baltic approaches against the current. Expanding the force still required trained submariners, and losing a boat often meant losing its entire crew, a problem for recruitment as well as procurement.
Notable Point · 6:56:30-7:00:25
Earlier U-class orders and the difficulty of expanding submarine crews
The case for earlier and larger U-class orders rests on predictable wartime losses, coastal requirements, and the difficulty of replacing trained crews.