South Arabia during World War I

Campaign in South Arabia
	Part of Middle Eastern theatre of World War I
	; A QF 15 pounder emplacement of B Battery, Honourable Artillery Company at Sheik Othman in 1915
Date	10 November 1914 – 31 March 1919
Location	Southern-western and western South Arabia (modern-day Yemen)
Result	Stalemate Ottoman occupation of Lahij; British retention of Aden;
Belligerents
Ottoman Empire Imams of Yemen; Haushabi Sultanate; Ahl Haydara Mansur tribe; Kingdom of Yemen (from 1918)	United Kingdom India; New Zealand; Aden Protectorate Lahej; Fadhli Sultanate; Baidah Sultanate; Emirate of Asir;
Commanders and leaders
Ahmet Tevfik Pasha; (Commander of the VII Corps); Ali Sait Pasha; (Taiz Operational Region); Hüseyin Ragıp Bey ; (Tihamah Operational Region); Imam Yahya;	H. V. Cox; (Commander of the 29th Indian Brigade); D. G. L. Shaw; (Commander of the Aden Brigade); George J. Younghusband; (Commander of the Aden Brigade); Fadhl ibn Ali al Abdali †; Muhammad ibn Ali al-Idrisi;
Strength
14,000 Ottoman regulars; Yemeni irregulars	34,500 (total)
Casualties and losses
500–1,000 casualties	1,263+; 647 killed or missing; 32 captured; 584+ wounded

The campaign in South Arabia during World War I was a minor military campaign for control of the port city of Aden, an important way station for ships on their way from Asia to the Suez Canal. The British Empire declared war on the Ottoman Empire on 5 November 1914, and the Ottomans responded with their own declaration on 11 November. From the beginning, the Ottomans had planned an invasion of Britain's Aden Protectorate in cooperation with the local Arab tribes. The Ottomans had gathered in some strength on the Cheikh Saïd, a peninsula which juts out into the Red Sea towards the island of Perim.

At the start of the war, the British had one force stationed in the Aden Protectorate, the Aden Brigade, which was part of the British Indian Army. In November 1914, an Ottoman force from Yemen attacked Aden, but was driven off by the Brigade. The last Ottoman troops surrendered in March 1919.