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.McKenzie, F. A. "The Defence of India". The Great War: The Standard History of the All-Europe Conflict. H. W. Wilson, ed. Vol. 7, chapt. 128. This text is now in the public domain.

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.Richard J. Shuster, "Aden". The Encyclopedia of World War I: A Political, Social and Military History, Volume 1, Spencer C. Tucker, ed. (Santa Barbara: ABC-CLIO, 2005), p. 37. The last Ottoman troops surrendered in March 1919.

Background

Opening of the Front The Ottoman Empire had been engaged in a diplomatic and territorial rivalry in Yemen with Great Britain -which had occupied Aden in 1839- until 1914. This competition occasionally resulted in localized armed skirmishes. In March 1914, following a period of diplomatic negotiations, the two powers signed a boundary agreement. This treaty partitioned the Yemeni territories into Ottoman and British spheres of influence, a division that would largely define the region's political geography until the late 20th century.

At the outbreak of World War I in August 1914, the Ottoman Empire and the British Aden Protectorate shared a direct land border. Given the strategic importance of the region, both administrations monitored the border closely. While the Ottoman Empire initially maintained a neutral stance, its subsequent entry into the war on the side of the Central Powers made a conflict in Yemen increasingly probable.

Mahmut Nedim Bey, the last Ottoman Governor of Yemen, noted that the decision to initiate hostilities was made in consultation with Ali Sait Bey, commander of the VII Corps. Regarding the mobilization and the breach of the 1914 border agreement, Mahmut Nedim stated:

Ottoman archival records suggest that tensions escalated following British maritime activity along the Yemeni coast. British authorities in the Aden Protectorate, concerned by Ottoman military movements in the vicinity of Al-Hudaydah, had discussed the possibility of naval strikes as early as August 1914, contingent upon "hostile Ottoman intent."The National Archives (TNA), Foreign Office (FO), 371/2134. Following the Black Sea raid and the formal commencement of hostilities between the Ottoman Empire and the Entente, a British gunboat arrived off Hodeidah in early November 1914 and sank two Ottoman vessels.

The raid on Hudaydah served as a catalyst for the total breakdown of diplomatic relations in the region. Ottoman authorities protested the action and placed pressure on the British consulate, while the British Consul formally announced the cessation of relations with the Yemen Vilayet. Consequently, the VII Corps was placed on full alert, and military operations were initiated throughout the Yemen Front.

Command and forces on the front and Center of gravity

British forces British forces defending the Aden Protectorate were initially centered around the Aden Brigade, commanded successively by D. G. L. Shaw and George J. Younghusband, and later reinforced by the 29th Indian Brigade under H. V. Cox.

Ottoman Forces The VII Corps was stationed in Sanaa, the center of the Yemen vilayet. When World War I broke out, it was directly attached to the Ministry of War along with its two divisions (the 39th and 40th Divisions). Therefore, when a front opened in Yemen, the Ottoman armies would achieve operational mobility through these two divisions. In later dates, the VII Corps would administratively be attached to the Fourth Army, yet it would continue to correspond directly with the Ministry of War.

The Yemen Front was planned to be conducted by being divided into two distinct sub-fronts. The 39th Division, which was to be stationed in the city of Ta'iz, targeted the British directly and the tribes under their protectorate. The operation to be conducted by this division was organized under the name "Ta'iz Mıntıkatü'l-Harekâtı" (Ta'iz Area of Operations). The 40th Division, which was to be stationed in Hodeidah, was tasked with confronting both potential amphibious assaults from the sea and pro-British tribes. The area where the 40th Division was located was designated as the Tihama Area of Operations Command.Mehmed Emin, Harb-i Umumi'de Osmanlı Cepheleri Vekâyi, p. 61. Mirliva Ali Sait Pasha was appointed to command the 39th Division, and Miralay Hüseyin Ragıp Pasha to the 40th Division, by Mirliva Ahmet Tevfik Pasha, commander of the VII Corps.

The most critical and active sector of the front was the military operations area organized by the Ta'iz Area of Operations. Setting aside tribal attacks, since there was no landing from the coastal side, that is, directly by the British, no military engagement with the British occurred in the Tihama region. However, the region occupied by the 39th Division witnessed severe military engagements toward both Bab-el-Mandeb and Aden.

Further north, the Hejaz Expeditionary Force remained under the independent command of Omer Fakhri Pasha.

Capture of Cheikh Saïd

The 29th Indian Brigade, under Brigadier-General H. V. Cox, CB, then on its way from India to Suez, was ordered to interrupt its voyage to capture Cheikh Saïd and destroy the Ottoman works, armaments, and wells there. On 10 November 1914, transports conveying three battalions of the 29th Indian Brigade and the 23rd Sikh Pioneers arrived off the coast of the peninsula. They were accompanied by the armoured cruiser HMS Duke of Edinburgh, which opened fire on the Ottoman defences while the transports were seeking a satisfactory landing-place. The point that had been at first selected proved impossible on account of the weather, and the troops had to land a little way off under the cover of the fire of the cruiser. They stormed the Ottomans' positions and compelled them to retreat, leaving their field guns behind. The sailors took active part in the fighting with the troops, and a naval demolition party assisted, on 11 November, in destroying the Ottoman fortifications. Having accomplished its task, the British force re-embarked and continued on to Suez. It was not considered advisable at this time to push an expedition inland. The Ottomans, consequently, retained some forces on the northern boundary of the Aden Protectorate.

Seven months later they reoccupied Cheikh Saïd and endeavoured from there to effect a landing on the north coast of Perim. This attack was successfully repulsed by the garrison of the island, the 23rd Sikh Pioneers.

Land campaign

Offensives on Baidah On 2 February 1915, the Ottoman Empire invaded the Baidah Sultanate. The Haushabi sent a large force in support of the Baidah Sultan. By the 13th, the Baidah had routed the Ottomans and captured their tents and ammunition. Sometime before the 20th, the Ottomans returned and raided Baidah's outlying villages, before being chased away by a Baidahni force of 1,000 troops, suffering 10 killed and many wounded, as well as losing 3 camels filled with ammunition, shells and tents. The Baidah Sultan expected that the Ottomans would invade again and declared to Britain his intention to defend his country to the last. On his request, Britain sent him ammunition.

On 21 March 1916, Zaidi forces loyal to the Ottoman Empire launched another offensive into the Baidah Sultanate, intending to use Baidah as a springboard for further offensives onto Shihr and Mukalla. Recognizing the threat posed, Britain sent 200 rifles and 30,000 rounds of ammunition to the Baidah Sultan in support. The attack ultimately failed.

Battle of Ad-Dakim

Sultanate of Lahij In July 1915 an Ottoman force from North Yemen crossed the frontier of the Aden hinterland and advanced towards Lahij, which was at this time one of the most important towns in South Arabia and the capital of the Abdali Sultanate of Lahij (Lahaj). Placed in an oasis, surrounded by a fertile plain with the deserts beyond, it was the centre of trade between Aden, a British crown colony, and its hinterland, the princely states under a protectorate. In the years leading up to the war, relations between Britain and Lahij had been friendly, the British paying the sultan a subsidy for the occupation of certain land in the interior and protecting him and his agricultural people against the tribes of the desert, who frequently raided them. Propagandising during the war, British historian F. A. McKenzie wrote of the sultan: Under our protection the Sultan of Lahaj had waxed very prosperous. His city, with its palace, its gallows— built for ornament rather than use—its purely Oriental life, its fine horses, its little show army, and its constant traffic in camels and caravans, seemed like a vision out of the Arabian Nights. When war broke out the Abdali Sultan proved that his loyalty to Britain was real. Though other tribes turned against us he came to our side and prepared to help us. He soon made himself an object of special detestation to the [Ottoman] and to many of the surrounding tribes by his open and unwavering friendship for Britain.

Siege The sultan sent word to General D. G. L. Shaw, commanding the Aden Brigade, that the Ottomans were advancing from Mawiyah to attack him, and asked for help. General Shaw ordered the Aden Movable Column, under Lieutenant-Colonel H. E. A. Pearson, towards Lahij. The Aden Camel Troop was despatched to reconnoitre. It discovered a strong Ottoman force beyond Lahij, supported by a large number of Arab tribesmen. The Camel Troop fell back on Lahij, where it was reinforced by the advance guard of the Movable Column, numbering two hundred and fifty rifles, with two ten-pounder guns. This advance guard had moved up under most trying conditions. The heat was intense, there was great shortage of water, and progress was difficult over the sand. The main body of the Column was so delayed by difficulties of transport and by shortage of water that it did not reach Lahij at all.

The British in the sultan's capital found themselves faced by several thousand Ottoman troops and twenty guns. In addition, Arab tribesmen had rallied by the thousand to help the Ottomans. The British were backed by the few hundred men of the sultan of Lahij's native army. The Arab camp-followers of the Aden detachment deserted them in a body at the most critical hour, taking with them all their camels. Fighting opened on the evening of Sunday, 4 July. The Ottoman forces made several attacks against the British line, but each was driven off. Although after the battle the efforts of the Royal Artillery drew a tribute from General Shaw, the superior Ottoman artillery had kindled fires in different parts of Lahij, and the British were in danger of being outflanked and cut off by the Arab tribal horsemen. The sultan was killed with many of his men. When the main Aden Column never arrived, the British withdrew on 5 July with the loss of three officers wounded, but the main loss was not so much in men as in prestige.

Analysis