Three days before the Dec. 7, 1941 Japanese attack on Pearl Harbor, President Roosevelt was warned in a memo from naval intelligence that Tokyo's military and spy network was focused on Hawaii. In the newly revealed 20-page memo from FDR's declassified FBI file, the Office of Naval Intelligence on December 4 warned, In anticipation of open conflict with this country, Japan is vigorously utilizing every available agency to secure military, naval and commercial information, paying particular attention to the West Coast, the Panama Canal and the Territory of Hawaii." The memo, published in the new book December 1941: 31 Days that Changed America and Saved the World went on to say that the Japanese were collecting "detailed technical information" that would be specifically used by its navy. To collect and analyze information, they were building a network of spies through their U.S. embassies and consulates. Historian and acclaimed Reagan biographer Craig Shirley, author of the just released December 1941, doesn't blame FDR for blowing it, but instead [said] that it "does suggest that there were more pieces to the puzzle" that the administration missed. He compares the missed signals leading up to Japan's attack to 9/11, which government investigations also show that the Clinton and Bush administrations missed clear signals that an attack was coming. "So many mistakes through so many levels of Washington," said Shirley. "Some things never change."