Meuse – BATTLE OF ST MIHIEL (until September 16): After 4-hour barrage from 0100 hours by 3,010 guns, 216,000 men of (10 divisions) US First Army (Pershing), supported by 48,000 French (4 divisions) advance in heavy rain 5 miles on 12-mile front vs Fuchs’ 75,000-strong Detachment C (already withdrawing its 13 divisions) and take 8,000 PoWs. AEF fires 100,000 round (200t) phosgene; 9000 gassed (50 deaths). Patton and MacArthur meet under fire, former outwalks his tanks (70 of 174 reach startline).
Cambrai – BATTLES OF THE HINDENBURG LINE BEGIN: Battle of Havrincourt won on 5-mile front by 6 divisions of Byng’s Third Army who take village southwest of Cambrai, 1,000 PoWs and beat 4 division counter-attacks.
Western Front – St Mihiel Operation: Greatest Allied air concentration of war with US units; 25 French escadrilles; le Division Aerienne (600 aircraft) and 9 squadrons of Independence Force (c.100 bombers); single Italian, Brazilian, Portuguese, Belgian squadrons. Total 1,483 planes under US Brigade-General Mitchell, bombers and recon planes spearhead Pershing’s advance while fighters maintain local air supremacy (‘barrier’ technique, as pioneered at Verdun). US 3rd Pursuit Group specializes in lorry-busting. Rickenbacker shoots down JG2 Fokker (6th kill), but JG2 claims 81 victories for 2 losses (September 12-18).
Russia: Tukachevksi’s Red First Army retakes Simbirsk, Lenin cables Trotsky with thanks.
East Atlantic: U-boat sinks Union liner Galway Castle (154 lives lost).
Mediterranean: Armed boarding steamer Samia sunk by U-boat.