Ypres – Battle of Bellewaarde Ridge (until May 25): 4 German divisions attack, capture Mouse-trap Farm, but lose other gains despite a 4 1/2-mile wide gas cloud at 0245 hours against British 28th Division with 4th and 1st Cavalry Divisions (in use as dismounted infantry).
Galicia: Mackensen resumes offensive, destroys V Caucasus Corps reaching 11 miles east of San until next day and takes 21,000 PoWs, 39 guns and 49 MGs. Südarmee‘s Battle of Stryj (until June 11) successful by May 31 against Russian Eleventh Army.
Austro-Italian frontier: Italian Carnic Group capture Plöchen Pass and frontier peaks but does not exploit against Austrian VII Corps.
Gallipoli: 10-hours ANZAC armistice to bury 3,000 Turk dead. At Helles bridgehead 3 British divisions form a Corps (numbered VIII on June 5).
Morocco: Lyautey given Arabic letter containing German appeal for revolt on May 29. Rebel chief Abt el-Selam submits to him at Casablanca in June.
Adria: Austrian Fleet from Pola bombards Ancona, Porto Corsini, Rimini, Senigallia and railways and bridges on Italian coast. Flying boats raid Venice and Chiaravalle airship sheds. Italian destroyer Turbine sunk off Pelagosa island by cruiser Heligoland and 3 Austrian destroyers.