From the mid-19th century, the yeomanry's policing role diminished with the establishment of a civilian police force, and renewed fears of invasion turned its focus to national defence. The Royal Gloucestershire Hussars' first battle honour was won in South Africa during the Second Boer War, when a contingent of Gloucestershire yeomanry served as mounted infantry in the Imperial Yeomanry. Before the First World War, all volunteer forces, including the yeomanry, were brought into the Territorial Force. On the outbreak of the war the regiment raised a second-line unit, which remained in the UK and became a cyclist unit in 1916, and a third-line unit, which served as a reserve. The first-line unit saw action as infantry at Gallipoli and as cavalry in the Sinai and Palestine Campaign; in the latter it fought both mounted and dismounted from the Suez Canal to Aleppo in modern-day Syria. Following the war, the regiment was downsized and converted to the 21st (Royal Gloucestershire Hussars) Armoured Car Company.