With the outbreak of the
First Anglo-Afghan War in 1839 Chamberlain's active service began. He was present at the
siege of Ghazni (23 July 1839) and at the operations around
Kandahar. In September 1841 he was appointed to the command of the
5th Janbaz cavalry, and in the following month, he became adjutant of
Christie's horse. Until the end of the Afghan campaign, he was engaged in constant heavy fighting. In 1843 Chamberlain was sent to
Scinde with two squadrons of Christie's horse as an independent command, to be known as Chamberlain's horse. In 1845 he was invalided to the
Cape of Good Hope, where he married. Next year he returned to India as second in command of the 9th irregular cavalry, into which his own corps had been absorbed. During the
First Anglo-Sikh War and the
Second Anglo-Sikh War he was constantly in action. He was at the
battle of Chillian walla on 13 January 1849, receiving the medal and clasp. On 30 January he was again engaged in the neighbourhood; here he was wounded and was made the subject of a special despatch by
Lord Gough (31 January). At the
Battle of Gujrat on 21 February, he had to be lifted into the saddle, where he remained throughout the day. He was awarded the clasp, was
mentioned in despatches, and, being promoted to captain and
brevet major in November 1849, was given the command of the 1st irregular cavalry, formerly
Skinner's Horse. He served with them in the
Mohmand expedition of 1854 and received a medal and clasp. ==Indian Rebellion of 1857==