Gerry asks in comments:
Wasn't there a Japanese General or some such who said that invading the USA was stupid and suicidal because there would be a rifle behind every blade of grass?Yeah, Gerry, that quote is attributed to Japanese Admiral Isoruku Yamamoto, although serious scholars believe that it is erroneously attributed. Yamamoto was the Commander in Chief of the Imperial Japanese Navy and was one of the main architects of the attack on Pearl Harbor. He was also a graduate of Harvard University and the US Naval War College. Yamamoto had spent a considerable amount of time in the United States and understood our military capacity. Yamamoto was killed in 1943 near the Solomon Islands when his transport plane was ambushed by P-38 fighter planes. His death was a serious blow to Japanese morale at the time.
There's also no evidence that he made the statement that "I fear that all we've done is awakened a sleeping giant and filled it with a terrible resolve." It's a great line, but it has no citation except the movie Tora, Tora, Tora.
Yamamoto is quoted as saying "In the first six to twelve months of a war with the United States and Great Britain I will run wild and win victory upon victory. But then, if the war continues after that, I have no expectation of success."
Yamamoto was an interesting guy and the question is if he had lived, would he have counseled to let the war continue when it was apparent that Japan would lose? We'll never know.