Watch on the Rhine
Apr 1 Lillian Hellman's play "Watch on the Rhine" premieres in NYC
- Apr 1 Nazis forbid Jewish access to cafés
- Apr 1 Pro-German Rashid Ali al-Ghailani grabs power in Iraq
- Apr 1 The Blockade Runner Badge for German Kriegsmarine is instituted.
- Apr 1 US Navy takes over Treasure Island in San Francisco Bay
- Apr 2 German occupier disallows Dutch scouting association
Churchill Warns Stalin
Apr 3 British Prime Minister Winston Churchill warns Soviet leader Joseph Stalin that a German invasion is imminent
8th US Masters
Apr 6 8th US Masters Tournament, Augusta National GC: Craig Wood wins his first major title, 3 strokes ahead of runner-up Byron Nelson; Masters' first wire-to-wire champion
- Apr 6 Beginning of operation Bestrafung - German bombers attack Belgrade (17,000 die)
- Apr 6 British major general Michael Gambier-Parry captured in North Africa
- Apr 6 German bombardment of Piraeus (munitions ship explodes)
- Apr 6 Italian forces holding Addis Ababa surrender to British & Ethiopian forces
- Apr 7 British generals O'Connor & Neame captured in North Africa
Croatia German Puppet Statete
Apr 10 Independent State of Croatia led by Ante Pavelić established as fascist German puppet state
- Apr 11 Jewish Weekly newspaper taken control by Nazis
- Apr 11 Nazi occupiers in Netherlands confiscate Jewish assets
- Apr 12 Stanley Cup Final, Olympia Stadium, Detroit, MI: Boston Bruins defeat Detroit Red Wings, 3-1 for a 4-0 series sweep
Darlan Consults with Hitler
Apr 12 Vichy-France's head of government Admiral François Darlan consults with Adolf Hitler
- Apr 13 Heavy German assault on Tobruk
- Apr 13 Pact of neutrality between the USSR and Japan is signed.
- Apr 14 1st massive German raid in Paris, 3,600 Jews rounded up
- Apr 14 45th Boston Marathon won by Leslie Pawson in 2:30:38; his third victory in the event
- Apr 14 King Peter leaves Yugoslavia
- Apr 15 1st helicopter flight of 1 hr duration, Stratford, Ct
- Apr 16 Little Theater at Adelphi Strand, London closes
- Apr 17 British troop land in Iraq
- Apr 17 Egyptian steamer SS Zamzam attacked and later scuttled by German cruiser Atlantis (all on board rescued)
- Apr 17 US Office of Price Administration forms (handled rationing)
- Apr 17 World War II: The Kingdom of Yugoslavia surrenders to Germany.
Mother Courage and her Children
Apr 19 Bertolt Brecht's play "Mother Courage and her Children" premieres in Zurich
- Apr 19 Bulgarian troops invade Macedonia
- Apr 19 Milk rationed in Holland
- Apr 20 100 German bombers attack Athens
- Apr 20 Dodgers start to wear liners in their caps
- Apr 21 WWII: Greece surrenders to Nazi Germany
- Apr 23 Greek Army surrenders to Germany; British RAF evacuates the Greek King George II to Egypt
- Apr 24 British army begins evacuation of Greece
- Apr 24 Dutch Prince Bernhard becomes an RAF pilot
Operation Mercury
Apr 25 Operation Mercury: Adolf Hitler orders the conquest of the island of Crete, the first mainly airborne invasion in military history