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. 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. Instead Dundas, after witnessing Prussian army manoeuvres in Silesia in 1784, favoured the army model that Frederick the Great had created. Its use of drilled battalions of line infantry marching in formation was a stark contrast to the light brigades that fought in small independent groups and with cover during the American War of Independence.
Later career
On 23 June 1789 he became Adjutant-General in Ireland where he was able deploy his ideas for military training. He was promoted to major-general on 1 May 1790 and, as Britain became involved in the French Revolutionary Wars, he was appointed second in command at the siege of Toulon under O’Hara and Lord Mulgrave from September 1793, where he commanded an abortive attack on the Arenes Heights on 30 November 1793. Dundas became commanding officer under Lord Hood after O’Hara’s capture in this action. He lost Fort Mulgrave and Mount Faron after a 3-day bombardment on 17 December 1793. Dundas commanded the initial expedition to Corsica in 1794, landing 7 February 1794 and capturing the Mortella Tower. Next, he captured the Port of San Fiorenzo and Bastia, an important first step ultimately leading to the capture of the island and establishment of a short-lived Anglo-Corsican Kingdom by forces under Hood and Admiral Lord Nelson. Hood forced Dundas to resign on 10 March 1794; Dundas transferred to serve in the Flanders Campaign under the Duke of York. 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. Dundas replaced Sir Robert Laurie at the head of his brigade during the retreat to Antwerp. In December, while commanding the British Right under Harcourt, he led the attack at Tuil on 30 December and directed the rearguard action at Geldermalsen on 5 January 1795. He was made commander of the British forces left behind at Bremen in April 1795 and given the local rank of brevet lieutenant general while remaining in Europe on 2 May 1795. On 26 December 1795 Dundas became Colonel of the 7th Light Dragoons and on 8 November 1796 he became Quartermaster-General to the Forces in which role he implemented the army's official drill book for Cavalry officers. He was promoted to the substantive rank of lieutenant-general on 4 February 1797. '', at which Dundas commanded the 3rd Division, during the Anglo-Russian invasion of Holland Dundas commanded the 3rd Division under the Duke of York in the Helder Campaign 1799, seeing action at Den Helder on 27 August, Zype on 10 September, Bergen on 19 September, Alkmaar on 2 October and Castricum on 6 October. On 15 February 1800 he was given the honorary appointment of Governor of Landguard Fort. He was made Colonel of 2nd Dragoons on 9 May 1801, promoted to general on 24 April 1802 and made commander in Kent and Sussex from 1803. Dundas was appointed Knight of the Order of the Bath on 28 April 1803 and went into semi-retirement in 1805. He became General Officer CommandingNorthern District in 1807 and, in that capacity, he was involved in suppressing a keelmen's strike on Tyneside. He chaired the hearing against Le Marchant on charges of calumny from 23 January 1807, was a member of the Court Martial that tried Whitelocke for the failure of the Buenos Aires expedition on 28 January 1808 and was a member of the Board of Enquiry of the Convention of Cintra in 1808. He was appointed Colonel-in-Chief of the 95th Foot on 31 August 1809. 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. Dundas was also a Privy councillor from 22 March 1809 and Colonel of the 1st Dragoon Guards from 27 January 1813. Dundas was Governor of the Royal Hospital Chelsea from 3 April 1804 until his death. Advanced to Knight Grand Cross of the Order of the Bath on 4 January 1815, he died at the Royal Hospital Chelsea on 18 February 1820 and is buried in the grounds.
Assessment
In the army Dundas was nicknamed "Old Pivot" for his Prussian-style drill books. Burne describes him as "A level-headed officer", but "cautious", while Bunbury writes "He...was an aged man...a brave, careful, and well-skilled soldier...Dundas was a tall, spare man, crabbed and austere, dry in his looks and demeanour...there were peculiarities in his habits and style which excited some ridicule amongst young officers. But though it appeared a little out of fashion, there was 'much care and valour in that Scotchman'". Thoumine writes that "Dundas was perhaps not as graceful nor as polished as some of his contemporaries, but he was as sound as oak and utterly reliable".
Family
In 1807 he married Charlotte De Lancey, daughter of General Oliver De Lancey; they had no children.
