Charles Mordaunt was born in 1658, the son of John, 1st Viscount Mordaunt (of Avalon and Baron Mordaunt of Reigate) and Elizabeth Carey (grand-daughter of 1st Earl of Monmouth). His father died on 5 June 1675 so he succeeded to the peerage as Viscount Mordaunt. He did not become Earl of Peterborough until 19 June 1697 when his uncle Henry, the 2nd Earl, died. Charles was educated at Tonbridge and Christ Church, Oxford. At the age of 16 he joined the Mediterranean Fleet and was in the expedition to Tangier. He then entered political life as an enthusiastic Whig, strongly opposed to the Catholic James Duke of York. When James became King, Charles hurried away to Holland. There he worked hard to persuade William or Orange to invade England. Eventually William was persuaded and Charles accompanied him to Torbay.
Viscount Mordaunt was now in a very favourable position, being so close to the monarch. He was appointed to the Privy Council in 1689, and in the same year was made First Lord of the Treasury and Earl of Monmouth. However he made some bad decisions and fell foul of King William so that he spent a brief period in the Tower of London in 1697. Some years after his release he proved politically troublesome so he was appointed Commander-in-Chief of land forces in Spain during the War of the Spanish Succession. He commanded in person at the siege of Barcelona and led the attack on the east side of Fort Montjuic. He was later criticised for lack of enthusiasm and lukewarm support for the Archduke Charles who the allies had placed on the Spanish throne. In his history of the Somerset Light Infantry, Sir Henry Everett had this to say of the Earl:
'Historians differ as to his abilities as a great military commander, though fame has given him a place among English soldiers of the period as second only to Marlborough. His previous military experience was chiefly at sea, but there was no exploit on this element to his credit which would lead one to suppose that he was fitted for supreme command of an important expedition. It is recorded that the siege of Barcelona was commenced against his advice, but when once decided on, he carried out the execution with commendable zeal. He was undoubtedly eccentric, vainglorious and quarrelsome. He appears to have hated foreigners, including his allies, and he despised Charles III whom he was commissioned to place on the throne of Spain. He was romantic, addicted to pleasure and the charms of the fair sex. Yet with all these drawbacks, he had undoubted military virtues, he was popular with his subordinates, and made the best use of the irregular Spaniards under his command, whom he thoroughly understood. He believed in and practiced mobility, he was a master in the minor stratagems of war, and appreciated the value of the elements of secrecy and surprise in his operations. To his credit it may be said that as long as he was in charge of the campaign in Eastern Spain the arms of the Allies were consistently victorious.'
While in Spain he had as one of the English regiments under his command, the 13th (Barrymore's) Regiment of Foot. He must have had a high regard for the regiment because he chose them to be transformed from infantry into dragoons. His sense of the dramatic became apparent when, in Jan 1706, the regiment paraded, totally unaware of what was in store for them. They were led, 500 of them, around a hill to find, on the other side, 500 horses all saddled and prepared for them. So for the next seven years one part of the 13th Regiment operated as dragoons and were known as Pearce's Dragoons. The Earl of Peterborough, by this act made one more enemy; the Colonel of the 13th, The Earl of Barrymore, who complained bitterly to Queen Anne that his regiment had been ruined.
On his return to England there were angry debates in the House of Lords where his military exploits divided opinion, but the end result was that he was thanked by the House. However, he was still regarded as a problem and sent off once more to Vienna. In August 1712 he was appointed Colonel of the Royal Horse Guards which lasted until June 1715. In 1713 he was appointed Knight of the Garter, but when George I ascended the throne of Britain on 1 Aug 1714 he lost any influence that he still had. He was married (1678) to Carey Fraser, a third cousin, and had three children, two of whom died in 1710. His wife Carey died in 1709, and in 1722 he secretly married Anastasia Robinson, an opera singer and Handel's favourite soprano. The Earl died in Lisbon on 25 October 1735 and his remains were buried at Turvey in Bedfordshire. The portrait is one of at least two painted of Charles Mordaunt by Sir Godfrey Kneller. This one was painted c1715 and is in the National Portrait Gallery.