Legend has it that Isoroku Yamamoto Commander-in-Chief of the Imperial Japanese Navy during WWII said You cannot invade the mainland United States. Press J to jump to the feed. Isoroku Yamamoto Yamamoto Shitty Quote Quotes A Russian General Officer who was being asked about the possibility of invading the US said no because there woul be a scoped rifle behind every tree. . Naval War College and Harvard University. This photo reminded Wes of the quote. The referenced letter is claimed to be in the extensive personal files of Gordon W. Would be a gun behind evay blade of grass. Of course it was originally stated in. You cannot invade the mainland United States. Isoroku Yamamoto 1884 - 04-04 1943 - 04-18 was a Fleet Admiral and Commander-in-Chief of the Imperial Japanese Navy IJN during World War II. There would be a rifle behind each blade of grass But this quote is unsubstantiated and almost certainly bogus...