The Admiralty came to expect as many as four Japanese battlecruisers of roughly 20,000 tons with 12-inch guns. Japan had considered ships in this broad category and later developed the B-65 concept, but the reported program was far larger and more immediate than reality. Similar French and German construction made the idea seem plausible, while British assumptions about Japanese attacks on trade reinforced it. The reading also asks whether agents supplied the battlecruiser reports that their case officers had signaled they wanted. The episode shows how an analyst's prior model of the enemy can distort intelligence collection.
Notable Point · 2:09:32-2:10:31
Confirmation bias and phantom Japanese battlecruisers
British expectations about commerce raiding and foreign large-cruiser programs helped turn limited Japanese B-65 work into reports of a much larger battlecruiser threat.