The 15th (Imperial Service) Cavalry Brigade was a brigade-sized formation that served alongside British Empire forces in the Sinai and Palestine campaign, during World War I.

The states of Kashmir, Idar and Kathiawar provided smaller detachments for the brigade, which was at times reinforced by other British Empire regiments and artillery batteries when on operations.

When in the field, the commander of the British Forces alongside which any Imperial Service Troops were serving was recognised as the higher legal authority in accordance with the act.

[3] The Imperial Service Troops included cavalry, infantry, artillery, sappers and transport regiments or battalions, with several states contributing both men and equipment.

During the 1900 Boxer Rebellion in China, part of the British relief force contingent was an Imperial Service Brigade, raised from the troops of Alwar, Bikaner and Jodhpur.

[5][nb 1] The Kathiawar Imperial Service Signal Troop, commanded by Captain Henry St. George Scott of the 4th Gurkha Rifles, were with brigade headquarters, with an establishment of one Indian officer and twenty-seven men of other ranks, including twelve despatch riders from Idar State.

The brigade regained its own third regiment in May 1918 when the Jodhpur Lancers, commanded by Colonel Thakur Pratap Singh Sardar Bahadur, which had been serving on the Western Front in France, arrived in the theatre.

The main body of the brigade arrived at Suez on 16 November, travelled by train to Ismailia two days later and started their first war-time patrols along the banks of the Sweet Water Canal.

About seven miles (11 km) east of Toussoum they located the Turkish forces, estimated to be between three or four brigades in strength, and captured twenty-five men and ninety camels.

[16] The brigade's next action was on 22 March when two squadrons of Hyderabad Lancers were included in a force sent to assault a Turkish formation of 800 infantry and 200 cavalry supported by artillery, entrenched ten miles (16 km) east of El Kubri.

After a short fight the Turkish withdrew; it had been intended that the Lancers would move to cut off their retreat but the soft terrain prevented them getting into position in time.

To counter this new threat to the canal, the whole brigade was moved to Kantarah and the next day advanced into the Sinai, but failed to locate any Turkish troops and returned to Ismailia.

In response the brigade crossed the canal that night supported by infantry and Egyptian artillery and advanced on El Hawawish, where the Turkish were believed to be located.

For the next few weeks the brigade sent patrols out into the Sinai until 14 April,[25] when they were ordered to relocate to Kantarah, where two days later Brigadier-General Cyril Rodney Harbord took over command.

By 13:00 the brigade was north of Gaza when the Mysore Lancers' leading squadron located the Turkish rearguard, which included a heavy machine-gun position.

[30] The brigade now came under command of XXI Corps and at 01:45 on 8 November was ordered to move west of Beit Hanun and link up with the Australian Mounted Division, which was advancing from the east.

The XXI Corps Cavalry Regiment and Mysore Lancers were ordered to encircle and cut off their retreat, however dug in Turkish positions at the Wadi Hesi once again halted the brigade advance.

Moving at their best speed, the brigade reached the high ground east of El Medjel by 14:30, capturing two artillery guns, rifles and ammunition en route.

[9] The next day the brigade was designated the Desert Mounted Corps reserve and concentrated two miles (3.2 km) to the west of the Ghoraniyeh bridgehead over the River Jordan.

[34] On the final day of the raid on Es Salt, on 4 May, the brigade, with the New Zealand Wellington Mounted Rifles Regiment attached, was ordered to cross the Jordan and form a defensive screen on the east bank to cover the withdrawal of the ANZAC Division.

In the following twelve days, the brigade patrolled to the east of the River Jordan, resulting in numerous contacts with the Turkish defenders, during which several prisoners and deserters were captured.

The Jodhpur Lancers would deploy in the open and wait further orders, while brigade headquarters and the remainder of the machine-gun squadron and the artillery battery would be to the north of Beled Esh Sheikh.

The attack commenced on time; the Jodhpur Lancers advanced in squadron columns in the face of heavy Turkish rifle and machine-gun fire.

The next day Lieutenant-Colonel Hyla Holden, a SSO with the Jodhpur Lancers, became the first Allied officer to enter Beirut, the Arab Revolt forces commanded by Sherif Hussein bin Ali arrived that same afternoon and assumed control of the local government.

[49] At Homs, the brigade rested for two days and on 19 October headed for Er Rastan, with orders to repair a bridge over the River Orontes, which had been destroyed by retreating Turkish forces.

[49] Intelligence from locals suggested that a force of 1,000 men with two small artillery guns were heading north out of Aleppo, so the brigade set off in pursuit.

[51] At 11:00, the leading two Jodhpur Lancers squadrons and a machine-gun section reached a position overlooking Haritan to the north of Aleppo when they came under Turkish small arms fire.

[53] The Mysore Lancers had also started their advance but moved further east to get into a position to charge after discovering the Turkish line was longer than expected, taking them out of range of their supporting machine-guns.

[52] The extent of the Turkish position had not been fully appreciated, and was now estimated to be held by a force of 3,000 infantry, 400 cavalry, up to twelve artillery guns and between thirty and forty machine-guns.

[66] The Port Tewfik Memorial was erected at the Suez Canal to commemorate the 4,000 Indian officers and soldiers killed during the Sinai and Palestine campaign who have no known grave.