The Imperial Mounted Division was formed in Egypt in January 1917 with four cavalry brigades: the Australian3rd and 4th Light Horse Brigades and the British 5th and 6th Mounted Brigades. Four British Territorial Force horse artillery batteries were assigned to the division to provide artillery support, one per brigade. XIX Brigade, Royal Horse Artillery was formed for the division with The batteries had been assigned to the 2nd South Midland, Nottinghamshire and Derbyshire, London, and South Eastern Mounted Brigades, respectively, at the outbreak of the war. Each was equipped with four Ehrhardt 15-pounder guns. All four batteries had originally gone out to Egypt with the 2nd Mounted Division in April 1915, but did not proceed to Gallipoli when the division was dismounted for service there. Instead, they variously served on the Suez Canal Defences, as part of the Western Frontier Force in the Senussi Campaign, or in Aden where B Battery, HAC and Berkshire, RHA fought a sharp action at Sheikh Othman that removed the Turkish threat to Aden for the rest of the war. They rejoined 2nd Mounted Division on its return from Gallipoli in December 1915, however, the dismemberment of the division began almost immediately as units were posted to the Western Frontier Force, Suez Canal Defences or to various other commands. In practice, the batteries were tactically attached to the mounted brigades, for example, Nottinghamshire RHA to the 3rd Light Horse Brigade and A Battery, HAC to the 4th Light Horse Brigade
Early service
The brigade, and its batteries, served with the Imperial Mounted Division in the Sinai and Palestine Campaign as part of the Desert Column. With the division, it took part in the advance across the Sinai. The batteries were re-equipped with four 18 pounders each in time for the First Battle of Gaza. They also took part in the Second Battle of Gaza.
Reorganised
In June 1917, the Desert Column was reorganised from two mounted divisions of four brigades each to three mounted divisions of three brigades each. Consequently, the British 6th Mounted Brigade, along with Berkshire RHA, was transferred from the Imperial to the Yeomanry Mounted Division on 27 June 1917. Berkshire RHA joined XX Brigade, RHA in the Yeomanry Mounted Division on 5 July. On 20 June 1917, the Imperial Mounted Division was redesignated as Australian Mounted Division as the majority of its troops were now Australian. On 12 August 1917, the Desert Column disappeared and the Desert Mounted Corps was formed. The batteries were still equipped with 18 pounders when the brigade was reorganised but were re-equipped with 13 pounders before the Third Battle of Gaza at the end of October 1917.
Later service
The brigade, and its batteries, served with the Australian Mounted Division throughout the rest of the Sinai and Palestine Campaign. As part of the Desert Mounted Corps, the division took part in the Third Battle of Gaza, in particular the Capture of Beersheba and the Battle of Mughar Ridge, and the defence of Jerusalem against the Turkish counter-attacks. In March 1918, the 5th Mounted Brigade left the division for the new 2nd Mounted Division and was replaced by the newly formed 5th Light Horse Brigade; B Battery, HAC was attached to the brigade. Still part of the Desert Mounted Corps, the division took part in the Second Trans-Jordan Raid. XIX Brigade, RHA supported the 4th Light Horse Brigade in the advance on the Jisr ed Damiye–Es Salt track on 30 April. The next day, a strong Turkish force attacked from the direction of Jisr ed Damiye and soon the artillery was in danger. B Battery, HAC was in the rear and managed to get away with all but one of their guns but the Nottinghamshire RHA and A Battery, HAC were less fortunate. Machine gun fire cut down the horse teams before the guns could be gotten away. XIX Brigade lost 9 guns in total, the only guns to be lost in action in the entire campaign. It final action was the capture of Damascus.
Dissolved
After the Armistice of Mudros, the division was withdrawn to Egypt and started to demobilise. The last of the Australians returned home in April and May 1919. A and B Batteries, HAC were reduced to cadre in Egypt on 25 October 1919 and the brigade headquarters was disbanded in Egypt on 30 October 1919.
