The British yeomanry during the First World War were part of the British Army reserve Territorial Force. Initially, in 1914, there were fifty-seven regiments and fourteen mounted brigades. Soon after the declaration of war, second and third line regiments were formed. However, the third line regiments were soon absorbed into the Cavalry Reserve Regiments, to supply replacements for the cavalry and yeomanry. Other horsed regiments in the British Army, during the war, were the regular cavalry regiments and the three regiments belonging to the special reserve: the North Irish Horse, the South Irish Horse and the King Edward's Horse. The senior yeomanry regiments could trace their origins back over 100 years; the oldest regiment, the Royal Wiltshire Yeomanry, had been formed in 1794. The most