In March 1917 the British mounted a major offensive into Palestine against the Turks. The first two failed attempts to break through at Gaza cost the British over 10,000 men - the Turks lost fewer than half that number. Then General Sir Edmund Allenby was put in charge, with orders to capture Jerusalem by Christmas. He shook up slack Allied commanders, trained his forces hard and built up their number to nearly 90,000, including the horsemen and camel-riders of the African Desert Mounted Corps. On 31 October 1917 Allenby broke through the Turkish defences at Gaza, capturing wells to supply his desert fighters with essential water. On 9 December the Allies entered Jerusalem.
Altogether around 140,000 British and 100,000 Indian troops took part in the Palestinian campaign against the Turks. It was the Indian cavalry, freed from their by now accustomed Western Front role as infantry and able to ride unhindered in the vast open landscapes of the region, who harried the Turks from the Sinai deserts through the Lebanon and Syria.
In 1918 Colonel T.E. Lawrence - 'Lawrence of Arabia' - undermined Turkish rule by instigating uprisings among the Arab leaders, while his flying guerrilla bands made frequent attacks on the Hejaz Railway, a vital communications link between Amman in Palestine and Medina in South Arabia.