Flanders: Alpenkorps together with 2 other divisions capture Bailleul and Wulverghem. Plumer evacuates 5 divisons from Passchendaele Ridge. Robillot’s French II Cavalry Corps (3 divisions) arrives near Cassel, 5 infantry divisions follow April 17-18.
Somme: Fierce artillery duel in Luce valley.
North Sea: 2 Royal Navy minelayers lay deep minefield 10 miles northeast of Laeso; escort destroyers Valentine and Virneira sink 10 German trawlers off Anholt island deep in Kattegat.
Adriatic: Admiral Horthy orders increased security at Pola. Allies begin to lay net barrage from Fano to Otranto (until September 30).
Britain: CAS Trenchard resigns; succeeded by Major-General Sir F Sykes.