Chatham joined the army as an ensign in the 47th Regiment of Foot on 14 March 1774. He served as aide-de-camp to General Guy Carleton in Quebec, but resigned his commission in 1776 in protest against the war with America, to which his father was vehemently opposed. He only returned to the army in March 1778, this time as a lieutenant in the 39th Regiment of Foot. He was due to sail to Gibraltar as aide-de-camp to the lieutenant governor, Colonel Robert Boyd, when his father collapsed mid-speech in the House of Lords and died shortly after. Having succeeded to the earldom, Chatham spent the following year in Gibraltar before transferring to the West Indies with a newly raised regiment, the 86th Foot. By the end of 1781 he was back in Britain and in 1782 obtained a captaincy in the London-based 3rd Regiment of Foot Guards. Although he was appointed colonel in October 1793 and major-general in February 1795, Chatham does not appear to have undertaken any military duties for nearly fifteen years after the end of the War of American Independence in 1783.
Political career
For much of the 1780s and 1790s Chatham focused on a political career. His brother, William Pitt the Younger, became prime minister in December 1783, and in July 1788 offered Chatham the cabinet post of First Lord of the Admiralty. 'I have had my doubts whether the public may not think this too much like monopoly,' Pitt confessed, 'but that doubt is not sufficient to counterbalance the personal comfort which will result from it and the general advantage to the whole of our system'. Pitt's cousin William Wyndham Grenville explained the reason for the appointment in more detail: Chatham would connect 'the department of the Admiralty with the rest of the administration, which has never yet been the case under Pitt's government, even in the smallest degree'. Chatham's tenure as First Lord of the Admiralty was not especially distinguished. Important reforms were shelved and Chatham soon acquired a reputation for disorganisation and laziness. Contemporaries noted 'the inconvenience attending his in bed till the day is advanced, as officers &c were kept waiting'. During the first major campaign of the French Revolutionary Wars Chatham's Admiralty was blamed in part for the failure of the 1793 siege of Dunkirk. Due to miscommunication between the Board of Ordnance and the Admiralty, the ships carrying siege weaponry and supplies for the besieging forces arrived two weeks late. Although in this instance Chatham does not seem to have been guilty of any neglect, his reputation was fatally compromised. It was around this time that he earned his nickname of 'the late Lord Chatham' due to his unpunctuality. Chatham nevertheless hung onto his office until the following December, when Pitt finally responded to pressure and moved his brother to the less responsible post of Lord Privy Seal. Two years later Chatham was promoted to Lord President of the Council. Here he stayed, remaining in office after Pitt's resignation under Henry Addington, until a cabinet reshuffle in June 1801 moved him to the post of Master-General of the Ordnance. He continued in this post until May 1810, with only a short interval out of office in 1806–1807. He became the General Officer in Command of the Eastern District in 1806.
In 1798 Chatham returned to the army. He was appointed to command a brigade in the Helder campaign in 1799. He was wounded by a spent ball at the Battle of Castricum on 6 October. After this he served as commander of various military districts, but for some reason was passed over in favour of Arthur Wellesley for a command in the Peninsular War. In May 1809 the Secretary of State for War, Lord Castlereagh, offered Chatham the command of an amphibious assault aimed at destroying the French fleet and fortifications around Antwerp and the island of Walcheren. Chatham commanded the largest expeditionary force Britain had yet fielded in the war. Despite early success in taking the town of Flushing, the campaign was an unmitigated disaster. The army made slow headway and the French immediately withdrew their fleet to Antwerp, a tactic that should have been foreseen by the politicians, admirals and generals planning the campaign from the start. While Chatham quarrelled with the naval commander, Sir Richard Strachan, as many as 8000 British troops succumbed to malaria. Chatham was recalled in disgrace. His appearance before a parliamentary enquiry did him no favours, particularly when it emerged that he had presented the King with a private memorandum which ought to have gone to the Secretary of State for War first. Spencer Perceval's government withdrew its support from Chatham and he was forced to resign from the Ordnance in May 1810. Chatham's political and military reputation was ruined. A poem circulated making fun of his inactivity and the lack of co-operation between the army and navy:
Chatham married The Hon. Mary Elizabeth Townshend, daughter of the 1st Baron Sydney, on 10 July 1783. The couple had no children. Lady Chatham died on 21 May 1821. Chatham did not remarry and on his death the Earldom of Chatham became extinct.
