Why convoy observers misread submarine attacks

What lessons about German attacks on convoys were repeatedly missed?

Accounts often assumed attacks came from outside the convoy, obscuring the possibility of submarines penetrating through its middle.

Convoy reports could produce false positives because observers began with the assumption that the threat approached from outside the formation. Demonstrations and exercises were needed to show how a submarine could move through the middle of a convoy and create a different pattern of sinkings. Many first-person accounts existed, but most were interpreted through the expected external-attack model. Operational evidence can be plentiful and still be misread when the initial model is wrong.