The Welsh Horse Yeomanry was a yeomanry regiment of the British Army that served in the First World War. The regiment was raised shortly after the outbreak of the war. Initially it served in East Anglia on anti-invasion duties, before being dismounted in 1915 and sent to take part in the Gallipoli Campaign. After withdrawal to Egypt, it was amalgamated with the 1/1st Montgomeryshire Yeomanry as the 25th (Montgomery and Welsh Horse Yeomanry) Battalion, Royal Welsh Fusiliers and served as such throughout the rest of the war. It took part in the Sinai and Palestine Campaign in 1917 and 1918, before being transferred to the Western Front where it remained until the end of the war. The regiment formed 2nd and 3rd Lines in 1914, but these never left the United Kingdom before being disbanded in 1