He was the seventh son of
Charles Cadogan, 1st Earl Cadogan by his second wife Mary Churchill, daughter of
Charles Churchill and Lady Mary Walpole, granddaughter of
Robert Walpole. Educated at
Eton, on 9August 1797 he became an
ensign,
by purchase, in the
18th Royal Irish Foot, which corps he joined at
Gibraltar after its return from
Tuscany, and obtained his lieutenancy therein in 1798. In 1799, having purchased a company in the
60th Regiment of Foot, he exchanged as lieutenant and captain to the
Coldstream Guards, and served therein until promoted to a majority in the
53rd Regiment of Foot in 1804. On 22August 1805 he became lieutenant-colonel in the 2nd battalion (afterwards disbanded) of his old corps, the 18th Royal Irish, having purchased every step. After serving with the battalion in Scotland and the Channel Islands, he left it when it proceeded to the island of
Curaçao, and exchanged, in 1808, to the
71st Highlanders at home. During the early part of the
Peninsular War, Cadogan served as
aide-de-camp to Sir
Arthur Wellesley, and after the passage of the
Douro was selected by him to proceed to the headquarters of the Spanish general,
Cuesta, to make arrangements for the co-operation of the English and Spanish armies in the forthcoming campaign on the
Tagus. He was afterwards present at the
Battle of Talavera. When the 71st Highlanders, then recently transformed into a light infantry corps, arrived in Portugal in the summer of 1810, Cadogan joined it at
Mafra and assumed command in succession to Colonel Peacocke. At its head he distinguished himself on various occasions during the subsequent campaigns, particularly at Fuentes de Oñoro, 5 May 1811, when he succeeded to the command of a brigade consisting of the 24th, 71st, and 79th regiments, at Arroyo dos Molinos 28 Oct. 1811, and at
Vittoria, 21 June 1813, where he fell. On the latter occasion the 71st was ordered to storm the heights above the village of Puebla, whereon rested the French left. While advancing to the charge at the head of his men Cadogan was mortally wounded. At his request he was moved so as to be able to witness the success of the charge before he died, aged 33. Cadogan was unmarried. Wellington, who was a friend, wrote of his merit and gallantry in his Vittoria despatch. ==Duel with Lord Paget==