Verdun: French Nieuport 11s of Esc N65 destroy 6 kite-balloons using very short-range firework-type rocket projectiles devised by French Navy Lieutenant Le Prieur.
Western Front: 2nd Lieutenant Ball forces down 2 German aircraft, his first successes (2 more combats on May 29).
Verdun: French 5th Division (Mangin) takes German trenches on 2,000-yard front Thiaumont Farm-Fort Douaumont and enters the fort after 11-minutes charge, captures most of it in 30 minutes.
Artois: BEF Reserve Army (Gough) formed, becomes Fifth Army on October 30.
Trentino: Austrian XVII Corps takes Bargo on river Brenta, completes advance as flank guard.
East Africa: Smuts resumes advance in 3 columns through Pare and Usambara Mountains, covers 130 miles until May 31.
Sudan – Battle of Beringia: Colonel Kelly’s 800 plus Egyptians and Sudanese auxiliaries (26 casualties), 8 guns and 14 MGs, which were advanced from Abaid since May 15, defeat Sultan of Darfur’s 5,000 strong attack (over 357 casualties) 12 miles northeast of El Fasher. Kelly occupies it on May 23, takes 4 guns and 55,000 cartridges.
Greece: Germany notifies Greek government that troops must enter Fort Rupel, evacuated under protest on May 27, Allies protest to Greece on May 31.
Germany: Finance Minister Dr Helfferich takes Interior and Deputy Chancellor portfolios as well. War Food Office (Batocki) I created, introduces food premiums for hard workers.