Brendan
Mounted Infantry ("M.I.") were widely used by the British army during the South African campaign. In 1888, Adjutant General Wolseley formed a series of Mounted Infantry schools; the concept meaning the training of an Infantry Section of 32 men and an officer from every line battalion as Mounted Infantry. Upon mobilisation, these sections were to come together to form two M.I. Battalions as a substitute for Divisional cavalry. The root idea appears to have come from the War Between the States (Civil War) in the US. As can be imagined, the Cavalry Lobby strongly resisted the idea of MI.
During the South African campaign, the British initially suffered a great shortage of mounted troops. Wanted were mounted men armed with infantry rifles and who would fight dismounted. Colonial units and the Imperial Yeomanry eased the shortage; however there were insufficient MI (except for small numbers) to take part in the Relief of Kimberley. Lord Roberts had ordained that MI companies were to be formed from every infantry battalion arriving in S.A. - to create eight new M.I.Battalions. A vast increase on the initial scheme. Various accounts show a that the actual formation of the M.I. Battalions was marked by much throwing of riders from horses. Nevertheless, when trained and in the field, the M.I. were an invaluable part of the British army. Indeed, in many respects, many of the regular cavalry regiments became M.I. in everything but name between 1900-1902.
Researching the activities of the M.I. can be difficult; due to reorganisations, unit numbering and the like.
I hope this has helped a bit. If you wish to read more, I would recommend "Doctrine and Reform in the British Cavalry, 1880-1918" by Stephen Badsley ISBN 978-0 7546-6474-3.
Regards
IL.