After the attack on Pearl Harbor, Hawaii, on December 7, 1941, many Americans anticipated further aggression from the Empire of Japan. Panic gripped the western states as fears of an invasion grew. Military authorities in the area sought to control the panic while implementing a plan for the defense of these states. Military leaders were convinced that Japanese saboteurs could cause significant damage. These saboteurs, it was believed, could come ashore and blend in with the local population of Japanese resident aliens or Americans of Japanese ancestry. Many people outside of the military shared this fear. Plans to detain and remove all people of Japanese ancestry from the area were formed by the military.