The RHA was responsible for light, mobile guns that provided firepower in support of the cavalry. It was the senior arm of the artillery, but the one that developed and grew least during the Great War. In 1914 the establishment of the RHA was one battery to each brigade of cavalry. A battery had six 13-pounder field guns and included 5 officers and 200 men. Motive power was supplied by the battery's 228 horses. The original BEF included only one division of cavalry of 4 brigades, and thus it had four batteries RHA, which were organised into two brigades