A good chunk of “Tora Tora Tora” is about how the US got so good at decoding Japanese diplomatic messages, they found out about the impending declaration before the Japanese ambassador’s staff was able to type it out themselves. They then showed how a message was sent from the decoders to the command staff, but failed to note the urgency of it and so it didn’t get delivered until after the attack.
I got the impression that the Japanese ambassador was unable to finish decoding and retyping the declaration in time because there was no one on staff with clearance to read the code that could type fast enough. They had received the code ordering them to deliver the message before the attack was actually going to happen, but ended up at least an hour behind.
Nevertheless, the message that was being sent wasn’t actually a declaration of war, but a final ultimatum. In that they were planning on executing an attack within an hour of issuing an ultimatum in a time where sending a message to recall the attackers would not be possible if the US for some reason finally relented, the Japanese clearly showed that they had no intention of doing anything but conducting a sneak attack. The official declaration of war did not come until the next day, so it would have been something of a sneak attack even if the final ultimatum had been delivered in time. If it had been, they could at least claim they gave ample time for letting the US know they would not tolerate any further the current relation status, but by the diplomatic message being as late as it was the attack was completely unjustified by traditional diplomatic practices.
I’ve noticed this before, but I have this tendency to not answer very many questions, but often have collateral information that relates to the answers people give.