Henry L. Stimson
US Secretary of War during the February 1942 Battle of Los Angeles. May have contributed to the military response by prepping America to receive "occasional blows" from the enemy.
Henry Stimson retired from public life in 1945, prior to the flying saucer craze of 1947. That said, as Secretary of War in 1942 he was involved in the Battle of Los Angeles incident. Stimson alleged that as many as 15 unidentified aircraft were seen flying over the city, which caused the U.S. Army and Navy to response with over 1,400 anti-aircraft artillery shells.
Stimson further alleged that these commercial aircraft were operated "by the enemy" from secret fields in California or Mexico. It's unknown if Stimson had any direct evidence to support his statements, or if this claim was formed to explain an overreaction from the U.S. Military.