German U-boats learned that convoy noise could mask them from escorts stationed outside the merchant formation. British analysts eventually recognized the tactic and placed an escort inside the convoy. The same noise now concealed the waiting escort from a submarine maneuvering among the columns. Merchant captains sometimes mistook that ship for a cowardly escort, even though its position had been chosen as a trap.
Notable Point · 1:36:53-1:38:44
The escort hidden inside the convoy
Once British analysts recognized that U-boats entered convoy columns to evade outer escorts, they placed an escort among the merchant ships to turn the German tactic into a trap.