Isoroku Yamamoto's sleeping giant quotation is a quote by the Japanese Admiral Isoroku Yamamoto regarding the 1941 attack on Pearl Harbor by forces of Imperial Japan.
The quotation is portrayed at the very end of the 1970 film Tora! Tora! Tora! as:

"I fear all we have done is to awaken a sleeping giant and fill him with a terrible resolve"

Although the quotation may well have encapsulated many of his real feelings about the attack, there is no printed evidence to prove Yamamoto made this statement or wrote it down. Wiki