One of the evidence was the
Battle of Okinawa (April to June 1945, just 2 months before the A-bomb was dropped), where everybody, including civilians, women, children and elderly fought the US troops or committed mass suicide, as they were told it was better than being taken prisoner by the barbaric Americans that would rape and torture them (it's only natural the Japanese would believe that, as it was the way the Japanese soliders treated the locals in conquered countries). This sole battle cost the lives of over 100,000 civilians and 76,000 soldiers. That's already more than Hiroshima and Nagasaki combined, and Okinawa is one of the least populous region of Japan !