[1] He exchanged to the 56th Foot as a lieutenant on 24 January 1756,[2] serving with this regiment during the Seven Years' War taking part in combined operations against the French ports of St. Malo and Cherbourg and fighting at the Battle of Saint Cast in September 1758.

[5] On 31 August 1783 Dundas left regimental service and became an advocate of officer training in the British Army, writing many manuals on the subject, the first being Principles of Military Movements published in 1788.

[6] He chose to play down the light infantry tactics that generals such as Lord Cornwallis or Willam Howe favoured during the American War of Independence.

[1] Appointed commander of the 2nd Cavalry brigade after the death of John Mansel at Beaumont on 26 April 1794, he distinguished himself at Willems on 10 May, and was attached to Otto's column at Tourcoing later that month.

[15][16] He was made commander of the British forces (mainly cavalry) left behind at Bremen in April 1795 and given the local rank of brevet lieutenant general while remaining in Europe on 2 May 1795.

[17] On 26 December 1795 Dundas became Colonel of the 7th Light Dragoons[18] and on 8 November 1796 he became Quartermaster-General to the Forces[19] in which role he implemented the army's official drill book for Cavalry officers.

[1] Dundas was Commander-in-Chief of the Forces from 1809 to 1811, during the Duke of York's period of disgrace following a scandal caused by the activities of his latest mistress, Mary Anne Clarke.

[30] Advanced to Knight Grand Cross of the Order of the Bath on 4 January 1815,[31] he died at the Royal Hospital Chelsea on 18 February 1820 and is buried in the grounds.