The intended delivery of Japan's declaration before the attack creates another test of strategic purpose. A timely warning would order Pearl Harbor to maximum alert, reducing surprise and making a crippling ambush less likely. More defenders and ships might survive, however, and successful resistance could give the fleet confidence to launch the advance Japan wanted to attrit. The same warning was therefore harmful to a destruction strategy but potentially useful to a lure, exposing the unresolved choice between them.
Notable Point · 29:59-31:06
A timely declaration would trade surprise for a stronger lure
Warning the United States before the strike would weaken an ambush but might leave more confident survivors able to sail west.