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

Isoroku Yamamoto's sleeping giant quotation is a film quote by the Japanese Admiral 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 producers of the film claim to have found the quote in Yamamoto's writings, there is no printed evidence to prove Yamamoto made this statement. Vermont C. Royster, the editor of the editorial page of 'The Wall Street Journal' from 1958 to 1971, offers a possible origin to the phrase attributed to Napoleon, "China is a sickly, sleeping giant. But when she awakes the world will tremble."