Formation The
Imperial Mounted Division was formed in Egypt in 1917 by bringing together two
Australian Light Horse brigades, two British
Yeomanry brigades, and a British
horse artillery brigade (four
batteries). These units were: • The
3rd Light Horse Brigade was formed in Australia in October 1914 with the
8th,
9th, and
10th Light Horse Regiments and was posted to Egypt in March 1915. It was dismounted and served in
Gallipoli from May to December attached to the
New Zealand and Australian Division (notably the
Battle of Sari Bair). It joined the
ANZAC Mounted Division when it was formed in March 1916 It joined the division on formation in January 1917; it was replaced in the ANZAC Mounted Division by the British
22nd Mounted Brigade. the 11th Light Horse Regiment was dismounted and served in Gallipoli as reinforcements to other regiments; the 12th Light Horse Regiment was dismounted and attached to the 3rd Light Horse Brigade in Gallipoli (AugustDecember 1915) and
2nd Light Horse Brigade in Egypt (April 1915January 1917); and the 13th Light Horse Regiment remained mounted and joined the
2nd Australian Division. The brigade was reformed in January 1917with the
4th Light Horse Regiment in place of the 13th and joined the division on formation. Shortly after the outbreak of war, it was assigned to the
2nd Mounted Division and moved to Egypt in April 1915. It was dismounted in August 1915 and took part in the
Gallipoli Campaign as 1st Mounted Brigade, notably the
Battle of Scimitar Hill. Due to losses and
wastage during August 1915, it formed a battalion sized unit1st South Midland Regimentin
1st Composite Mounted Brigade. It returned to Egypt in December where it was reformed and remounted. The 2nd Mounted Division was broken up in January 1916 and it served as Corps Troops from 21 January 1916 (numbered as 5th Mounted Brigade from April). It joined the division on formation. The
Queen's Own Dorset Yeomanry joined in the same month to replace them. The brigade's early service was identical to the 5th Mounted Brigade until January 1916 when it joined the
Western Frontier Force. All four batteries had originally gone out to Egypt with the 2nd Mounted Division in April 1915, but did not proceed to Gallipoli with the division. Instead, they variously served on the
Suez Canal Defences, as part of the Western Frontier Force in the
Senussi Campaign, or in
Aden where 1/B Battery HAC and 1/1st 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.
Ehrhardt 15-pounder guns but were re-equipped with more modern
18 pounders (four per battery) in time for the
First Battle of Gaza (2627 March 1917). In practice, the batteries were tactically attached to the mounted brigades, for example, 1/1st Nottinghamshire RHA to the 3rd Light Horse Brigade and 1/A Battery HAC to the 4th Light Horse Brigade. The division was also provided with support units, mostly assigned or attached directly to the brigades, but including an engineer
squadron, a signals squadron, and
train. ==Service history==