Tora, Tora, Tora was the Japanese code for maximum success in surprising the U.S.
Tora, Tora, Tora was Japanese code word to signal the beginning of the attack at Pearl Harbor 1941.
The "tora" is the two-syllable Japanese codeword used to indicate that complete surprise had been achieved: "to" is the initial syllable of "totsugeki, meaning "assault", while "ra" stands for "raigeki, meaning "torpedo attack".