In anticipation of service abroad, for which most of the men had volunteered, the regiment was vaccinated at the beginning of February and within 14 days, an epidemic of measles had broken out.
On April 6th orders were received to embark for Egypt to help guard the Suez Canal. On the following day, 26 officers, 507 other ranks, 498 horses, 56 mules along with machine-guns and vehicles, left Fakenham and arrived at Avonmouth to embark on the HMTs Karoa and Commodore, which set sail on the 9th and both had arrived at Alexandria by 21st April. It is recorded that during the voyage, 30 horses were lost.
After 4 months in Cairo, engaged on exercises and instruction on all aspects of warfare, official warning was received to prepare for service overseas as a dismounted unit. On 13th August two squadrons set sail for the Gallipoli Peninsula. The remaining squadron remained behind in Egypt to look after the horses.
Control of the Dardanelles, a stretch of water separating the Gallipoli Peninsula from mainland Turkey, was vital and in February 1915 a combined British and French fleet had attacked the outer forts of the Dardanelles and a bombardment was kept up until mid-April, by which time it was evident that ships alone were insufficient to overcome the shore batteries. On 25th of April a landing was made on the southern end of the Peninsula but, in spite of extreme gallantry of all concerned, no effective headway was made and by the end of July, it was evident that additional troops would be needed to avoid a stalemate of the situation.
On 17th August the Dorsets arrived in Lemnos harbour, from where the men were transported by barge to Suvla Bay, where they landed, quickly finding shelter from the constant firing from the well entrenched Turks on the surrounding hills. There in blistering heat and appalling conditions – often short of both rations and water and tormented by flies – it engaged over the next few months, a well fortified and determined enemy. The Battles of Chocolate and Scimitar Hills resulted in devastating losses for little territorial gain.
Gallipoli had become a stalemate and evacuation was the only realistic solution. On 31st. October the Dorsets left for Mudros and then returned to a relatively peaceful Egypt. However the Turks, emboldened by their success in Gallipoli had instigated a rebellion in Lybia, encouraging the local Senussi tribe to attack British interests in Egypt.
By the end of the year the Dorset Yeomen were encamped in the Western Desert, near Agagis, where the Senussi mounted a major attack, which was halted by a South African infantry unit. While the enemy main force withdrew, a rearguard group of 1,000 tribesmen supported by Turkish artillery, machine guns and leadership remained. On 26th February, the regiment, under its CO, Lt. Col Souter, determined to “help them on their way”, with the help of 8 armoured cars.. As the cars soon became bogged down in the sand, Souter ordered his men to mount and follow him. Three squadrons of the Yeomanry, with sabres drawn, (including, it is recorded, the cooks brandishing their meat cleavers) advanced on the fleeing Senussi, who were, by now some 1,200 yards away. As they closed, the Turkish officers rallied about 500 of the tribesman, to form a rearguard around three Maxim guns. For well over half a mile the cavalry advanced in two waves and the closer it got, the more the enemy lost their nerve; at approximately 50 yards the yeomen broke into a full gallop and most of the Senussi, scattered and ran. However at this point, Col Souter’s horse was shot from under him; a fate also suffered by Lt Blacksley and a number of yeomen. Undaunted they plunged in amongst the enemy with swords flashing. The Colonel however, was temporarily knocked unconscious; on coming round he found himself surrounded by a group of the enemy. Drawing his pistol, he held to the head of the man who appeared to be an officer, and ordered him to surrender, which he did. The officer turned out to be General Gaafar Pasha, the Turkish commander of the Sanussi and the rebellion quickly fizzled out.
For his action, Col Souter was awarded the DSO and a total of 20 MCs and 10 DCMs were awarded to others, for acts of bravery. This action had cost the Dorsets a quarter of their men and a third of their horses.