Berwick returned to England and was made Governor of Portsmouth. King James made him a Knight of the Garter, but due to the invasion of the Prince of Orange and the subsequent Glorious Revolution, the installation never took place. In the following year, James was overthrown and Berwick went into exile with him, taking an active part in the Irish campaign, including the Battle of the Boyne. After his father's final exile, Berwick served in the French army. He fought at the battles of Steenkerque and Landen. At the latter, Berwick was taken prisoner, but was exchanged for the Duke of Ormonde.
As a soldier, Berwick was highly esteemed for his courage, abilities and integrity. As a result of distinguished service in the War of the Spanish Succession, he became a French subject and was appointed a Marshal of France after his successful expedition against Nice in 1706. On 25 April1707, Berwick won the great and decisive victory of Almanza, where an Englishman at the head of a Franco-Spanish army defeated Ruvigny, a Frenchman at the head of an Anglo-Portuguese-Dutch army. After Almanza, Berwick was created Duc de Fitz-James in the Peerage of France by Louis XIV, and Duque de Liria y Xérica and Lieutenant of Aragon by Philip V of Spain. The last great event of the War of the Spanish Succession was the storming of Barcelona by Berwick, after a long siege, on 11 September1714.
Not long thereafter, Berwick was appointed military governor of the province of Guienne, where he became friendly with Montesquieu. In 1718 he found himself under the necessity of once more entering Spain with an army; and this time he had to fight against Philip V (War of the Quadruple Alliance). Many years of peace followed this campaign, and Berwick was not again called to serve in the field until 1733. In that year he was chosen to lead the Army of the Rhine in the War of the Polish Succession, but was killed by a cannon ball at the siege of Philippsburg, 12 June1734.
Berwick had children by both his marriages. His descendants were the French Ducs de Fitz-James and the Spanish Duques de Liria and later the Dukes of Alba.
