Achieving Surprise: Inconceivable Doesn't Mean What You Think It Means
How Japan Achieved Pearl Harbor Surprise
Japan's surprise attack on Pearl Harbor rested on novel operating concepts and effective deception. American knew how Japan would fight and didn't see anything in their sources of information.
U.S. naval intelligence was aware of Japan’s defensive outlook and had come to accept it as absolute. The Americans believed wholeheartedly that in any future conflict the majority of Emperor Hirohito’s naval forces would choose to remain in home waters rather than run the risk of leaving Japan undefended. ...
Among the changes resulting from this new direction was the organization of Japan’s carriers into a single unit. For more than a decade, the carriers had been arranged into divisions comprising two flattops and their escorts. In maneuvers, those divisions were parceled out to the various fleets to serve as escorts or scouts....
Communications security had been a major concern of the imperial navy as far back as the Russo-Japanese War, and it held the American and British radio intelligence offices in particularly high regard. It was for this reason that communication security was a feature of every navy exercise throughout the interwar period. ...
A complete lack of human intelligence sources meant that the Americans had no way to supplement, replace or verify the conflicting [radio intelligence] reports. The almost total reliance on intercepted radio traffic meant that all the Japanese had to do to give the Americans the slip was add new levels of security to their naval communications system.
So America knew Japan would operate on the strategic defensive to protect their home islands, knew Japan dispersed their aircraft carriers, and knew its own signals intelligence on the Japanese navy was good even if one-dimensional.
Admiral Yamamoto convinced his superiors to attack at the outset of war and to mass their aircraft carriers. And the Japanese conducted an extensive radio communications disinformation and concealment plan.
Seeing nothing from their prime source of information to contradict their assumptions about Japanese strategic outlook and operational practice, Americans assumed there was nothing to see.
Do read the linked article. The level of Japanese deception down to ensuring the "fists" of radio operators remained consistent during the period of the strike fleet massing and then approaching Hawaii is impressive. It's originally from 2006 but I don't recall reading it. I certainly don't remember knowing this information. We'll see if I remember this in 2042.
I think that this shows that drones and satellites don't rule out surprise, as Ukraine's August 2024 Kursk assault achieved. Reinforce enemy commander incorrect beliefs and they'll interpret what they see or don't see as supporting what they believe.
For God's sake—although I've been ridiculed for it—remember Pearl Harbor.