Sturgeon's friendly-fire scare exposes signal confusion

Sturgeon used the wartime recognition procedure, but the attacking aircraft apparently expected peacetime signals and dropped two bomb loads that missed. One conjecture, drawn from later reports, is that peacetime signals remained temporarily valid to protect submarines whose crews had not learned that war had begun. Delays in passing new instructions through Air Ministry and Coastal Command bureaucracy offer another possible cause. The episode shows how a correct signal can still fail when separate services do not share the same expectation at the moment of transition.