Related Clues:

• The U.S. joined it in 1941
• It included the RAF's "finest hour"
• Where DDE made his name
• Event with V-E Day and V-J Day
• The US joined it in '41
• Conflict during 43-Down's presidency, briefly
• 'Jojo Rabbit' setting: Abbr
• "Captain America: The First Avenger" backdrop, briefly