Dardanelles: U21 (Hersing) sinks British battleships Triumph (73 lost) off Gaba Tepe and Majestic (on May 27, 43 lost), capsizes in 7 minutes off Western Beach. U21 proceeds on to Constantinople after 4000-mile voyage.
Atlantic: U-boat torpedoes US SS Nebraskan but she reaches Liverpool.
Austro-Italian frontier: Italian 6th Infantry Division attacks in Chiese valley west of lake Garda but is easily held. 4 Austrian forts at Lavarone (southeast of Trento) shelled . Italian advance guard arrives on Isonzo.
Persia: Russians retake Urmia, occupy Miandab.
Gallipoli: 1st improved Anzac periscope rifle (Lieutenant-Corporal Beech) used at Quinn’s Post.
Cameroons: 1,290 Allies begin advance from Wumbiagas, fight 3 main actions, gain 12 miles in 19 days till blocked until June 13. Germans cut supply route on May 28, 60 British sick evacuated by May 31.
Sino-Japanese treaties grant Japan new treaty ports and 99-year Port Arthur lease.
Britain – COALITION GOVERNMENT: 12 Liberals and 8 Tories, Lloyd George Munitions Minister. 2nd Canadian Division formed.