Translations of encoded Japanese transmissions had a lag phase.
After the attack, obviously interest in WHAT IN HELL the Japanese were saying to their Embassies in the US became hugely interesting.
The last encrypted cables sent to Japanese Embassies in the US were chilling:
They addressed to topic of follow-up attacks on the US defense industrial base, calling on allies in the Japanese community.
US authorities could not disclose that, obviously, as the fact the US could read Japanese code was a very closely guarded secret; the enemy would instantly change their tactics. This topic is not talked about to this day, as the overwhelming majority of the ethic Japanese community was loyal to the US.
But not all were, and there was widespread worry about what could happen.
Germans and Italians were interned at Fort Meade, Maryland, where the NSA is now.
Another weird thing I learned only last year:
Very much of overseas Japanese intel collection during WW2 was secretly run out of the overseas Embassies of *SPAIN*.
Some historians state that bad actors working on behalf of the US framed up the Spanish for a ship explosion, then used that as pretext for the Spanish-American War, 40 years prior, leading to the loss by Spain of numerous overseas territories.
So Spain sorta “got us back”.
I greedily relished Yamamoto’s “We have awakened a sleeping giant” statement:
Alas, though he was a huge critic of Japan’s war drums and had studied at Harvard, he never actualy said those words.
People love that quote and it’s false. People aren’t going to want to hear that.
Yamamoto did, though, make numerous other statements warning of the possible or even likely course of the war on America.