Battle of the Somme– Battle of Flers-Courcelette (until September 22): From 0620 hours, after 40-minutes shelling, 14 divisions (2 Canandian and 1 NZ) and 32 of 49 FIRST TANK MK I‘s IN ACTION (5 ditched, 9 break down, 10 hit) advance 2,000-3,000 yards behind creeping barrage on 6-mile front capturing Flers, Martinpuich, Courcelette and High Wood by 1100 hours in German 3rd line. British Guards Division advance (Raymond Asquith, PM’s son, killed) towards Les Boeufs held up by ‘Quadrilateral’ (between Ginchy and Bouleux Wood).
French I Corps infantry advance at 1500 hours and make slight progress north of Priez Farm. Artillery and MG fire halt French movement near Rancourt.
Southern sector: French Tenth Army renews its attacks south of Somme on Santerre Plateau, captures 3 villages (until September 17) and repulses frequent counter-attacks. Micheler regrets lack of reserves prevents follow-up operations.
146 extra heavy guns sent to German First and Second Armies at the Somme and 144 wornout guns replaced (until October 8).
Hindenburg issues his first formal operation order: ‘The main task of the Armies is now to hold fast all positions on the Western, Eastern, Italian and Macedonian fronts and to employ all other available forces against Rumania’.
Romania: Crown Council decides to transfer half Transylvanian Armies to face Bulgaria.
Brusilov offensive – Pripet, Galicia: General Kaledin with Eighth Army HQ transferred south to command, troops between Lechitski and Sakharov, Gourko’s Special Army takes over Brusilov’s northern flank.
Dolomites: Monte Rosa Alpini Batallion captures Mt Cauriol (7,605 ft) at 4th assault, then Mt Gardinal (7,723 ft) to northeast (September 23), beats of Austrian attacks until September 28.
Adriatic – FIRST SUBMARINE SUNK BY AIR ATTACK: 2 Austrian Lohner flying-boats bomb and sink French submarine Foucault, then land and save crew.
Western Front: Royal Flying Corps helps engage 85 German batteries (29 silenced) and drops 8t bombs on 15 targets; claims 15 German aircraft, loses 14 aircrew and 6 aircraft. Second Lieutenant Ball destroys or forces down 10 German aircraft until September 28.
Southern Tunisia: – 4 French Farmans bomb Senussi base, but 1 crashes.