The Royal Sussex Regiment was a line infantry regiment of the British Army that was in existence from 1881 to 1966. The regiment was formed in 1881 as part of the Childers Reforms by the amalgamation of the 35th Regiment of Foot and the 107th Regiment of Foot. The regiment saw service in the Second Boer War, and both World War I and World War II.

The 2nd Infantry Brigade was a regional brigade of the British Army, active since before the First World War. It was the regional formation of the Army in the South East of England–the Brigade commanded and administered soldiers throughout Kent, Surrey and Sussex–but also Brunei. In December 2014 the Brigade merged with 145 (South) Brigade to form Headquarters 11th Infantry Brigade and Headquarters South East.