What were three missed opportunities to prevent the attack on Pearl Harbor?

Answer: The first warning of a possible Japanese attack on Pearl Harbor came in a coded cablegram from the U. S. ambassador to Japan, Joseph C. Grew, to the U. S. State Department on January 27, 1941. Grew's cable told of a report that "the Japanese military forces planned to attempt a surprise mass attack on Pearl Harbor." The Americans thought this was just a rumor and took no further action to investigate the claim. Other warning signs that occurred was on December 7th, at 3:52 a. m. when Minesweeper USS Condor spotted an unidentified submarine off the Honolulu harbor and notifies the destroyer USS Ward to investigate. They did not take into account that the US Navy had lost sight of a large Japanese fleet leaving Asia a week earlier. After investigating they found no further evidence of the sub in question.