1. Gavrio Prinzip, Serbian assassin of the Austro-Hungarian archduke Franz Ferdinand, dies in an Austrian fortress.
6. Rumania signs treaty of peace with Central Powers.
14. Italian naval forces enter the harbor of Pola and sink an Austrian battleship.
19. Major Raoul Lufbery, American aviator, shot down near Toul.
Australian troops capture Ville-sur-Ancre.
25-June 14. German submarines sink 19 ships off the Atlantic coast of the United States.
27. The Germans capture the Chemin des Dames ridge, regarded as impregnable, and sweep forward toward Paris on a 40-mile front.
28. The great German "victory drive" reaches the Aisne. The American First Division wins the battle of Cantigny, capturing the town in a brilliant attack, the first American offensive.
29. The Germans take Soissons, with 25,000 prisoners. Allied retreat continues.
30. German counter-attacks on Cantigny repulsed by the Americans. The Fifth and Sixth regiments, United States Marines, ordered to the Marne battle front where the Germans are nearest Paris.