Italy: Cadorna cancels 12th Isonzo offensive and starts defensive preparations, tells Allies this on September 20 who halt guns for the Italians on September 25.
Trentino: Italian battalions take 200 PoWs in Val Sugana but fail in dash for Trento inspired by Czech officer deserters (night September 18-19) at Carzano.
Channel: U-boat sinks destroyer HMS Contest (50 survivors).
Mediterranean: British patrol instructions advise limit of 12 ships per convoy with 4 escorts.
France: Painleve redefines French war aims as Alsace-Lorraine and reparations.