Assertion: tactic | /r/HasProperty | tried in october
Facets:
Source sentences:
text: Arm found the success of the pre-war trials had created some complacency; when these tactics were first tried in October 1939 (Hartmann's wolfpack) they were a failure; Hartmann found he was unable to exercise any tactical control from his boat at sea, and the convoy attack was unsuccessful, while three U-boats were lost in the operation.