The 2nd Line regiment was formed at Warwick in September 1914. In April 1915, it joined the 2/1st South Midland Mounted Brigade at Cirencester and in June moved to the King's Lynn area where the brigade joined the 2/2nd Mounted Division. On 14 July 1915, it was at Holkham and in October at Fakenham. On 31 March 1916, the remaining Mounted Brigades were ordered to be numbered in a single sequence and the brigade became the 10th Mounted Brigade (and the division 3rd Mounted Division) at Tunbridge Wells.