- Apr 1 Lillian Hellman's "Watch on the Rhine" premieres in NYC
- Apr 1 US Navy takes over Treasure Island in San Francisco Bay
- Apr 1 Nazis forbid Jews 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 2 German occupier disallows Dutch scouting association
Joseph Stalin
- Apr 3 Rasjid al-Gailani forms pro-German regime in Iraq
- Apr 3 Walton's overture "Scapino" premieres in Chicago
- Apr 4 German troops conquer Benghazi, Libya
- Apr 5 San Francisco Castro & Fillmore streetcars replaced by buses
- Apr 6 8th Masters Golf Tournament: Craig Wood wins, shooting a 280
- 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
Boxing Title Fight
- Apr 9 PGA establishes Golf Hall of Fame
- Apr 10 German troops conquer Libyan county Cyrenaica
- Apr 11 Germany blitzes Coventry, England
- Apr 11 Jewish Weekly newspaper taken control by Nazis
- Apr 11 Nazi occupiers in Netherlands confiscate Jewish assets
- Apr 12 Stanley Cup: Boston Bruins sweep Detroit Red Wings in 4 games
Event of Interest
Apr 12 Vichy-France's head of government Admiral Dalarn consults with Adolf Hitler
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 King Peter leaves Yugoslavia
- Apr 15 1st helicopter flight of 1 hr duration, Stratford, Ct
- Apr 16 Little Theater at Adelphi Strand closes
- Apr 17 British troop land in Iraq
- Apr 17 US Office of Price Administration forms (handled rationing)
- Apr 17 World War II: The Kingdom of Yugoslavia surrenders to Germany.
- Apr 19 45th Boston Marathon won by Leslie Pawson of RI in 2:30:38
- Apr 19 Bertolt Brecht's play "Mother Courage and her Childeren" 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 Greece surrenders to nazi-Germany
- Apr 23 Greece Army surrenders to German Nazis RAF brings Greek king George II to Egypt
- Apr 24 British army begins evacuation of Greece
- Apr 24 Dutch Prince Bernhard becomes an RAF pilot
- Apr 25 Operation Merkur: Hitler orders conquest of Kreta
- Apr 26 A tradition begins, 1st organ at a baseball stadium (Chicago Cubs)
- Apr 26 Potatoes rationed in Holland
- Apr 27 German troops occupy Athens, Greece
- Apr 28 Last British troops in Greece surrender