FILE - In this undated file photo, Japan's Emperor Hirohito rides a horse at the imperial palace in 1940. A newly released memo by a wartime Japanese official provides what a historian says is the first look at what was on the minds of Emperor Hirohito and Prime Minister Hideki Tojo on the eve of the fateful 1941 attach on Pearl Harbor that thrust the U.S. into World War II. (AP Photo, File)