Fortune was in our favor on this day.
Good fortune, and untold bravery.
Don't forget intelligence. According to the movie, and I believe it is correct in outline, this was crucial. It enabled what amounted to an ambush of the Japanese by the Americans.
I loved the scene in the movie where Charlton Heston was talking to Hal Holbrook, who was explaining their theories about the interecepted radio communications. Heston exclaimed in exasperation, "You're guessing!" Unperturbed, Holbrook replied, "We like to call it analysis."