Hi Adam

On 31 August 1939 the Kriegsmarine had 57 U-boats in service:
2 type IA, 6 type IIA, 18 type IIB, 6 type IIC, 10 type VIIA, 8 type VIIB, 7 type IX

14 boats were in training or not at sea:
4 school boats were used for training: U-1, U-2, U-8, U-11
6 boats were still in training: U-42, U-43, U-49, U-51, U-60, U-61
4 boats were in port: U-3, U-4, U-10, U-25

43 boats were at sea:
7 boats on patrol in Baltic Sea: U-14, U-18, U-22, U-31, U-32, U-35, U-57
3 boats on patrol in Kattegat: U-5, U-6, U-7
15 boats on patrol in North Sea: U-9, U-12, U-13, U-15, U-16, U-17, U-19, U-20, U-21, U-23, U-24, U-36, U-56, U-58, U-59
2 boats en route to North Atlantic: U-26, U-53
16 boats on patrol in North Atlantic: U-27, U-28, U-29, U-30, U-33, U-34, U-37, U-38, U-39, U-40, U-41, U-45, U-46, U-47, U-48, U-52

Those with known positions are shown if you enter the date on our page about the U-boat patrols: [uboat.net]

Best regards
Rainer

Crew member of uboat.net