The September war broke out

摘要

In 1935 an Anglo-German naval agreement was signed which allowed Germany to rebuild her navy, and the Kricgsmarine focused its attention on constructing a series of powerful surface ships. Meanwhile, U-I, the first U-boat constructed since World War I was commissioned in 1935, and the following year Karl Donitz became Commander-in-Chief of the German navy's U-boat arm.