The direct cause of u. s. involvement in world war ii was a) germany's invasion of poland. b) the japanese attack on pearl harbor. c) sinking of the lusitania by germany. d) italian mistreatment of foreign nationals by the us.

The correct answer is B. the Japanese attack on Pearl Harbor. The US didn't want to participate in the war even though there was heavy lobbying for it to join. When Japan attacked, they made a deal with the Allies that if they helped free Europe, the allies would help them defeat Japan. What ensured was D-Day and Normandy, followed by Russian Berlin sacking, and eventually when Europe warfare ended, everyone attacked Japan but the US decided to nuke them.