In 1839, after a decade of unrest in the Middle East, the Great Powers (Britain, Austria, France, Prussia & Russia) agreed to help Turkey recover her province of Syria which had been independent since an insurrection there in 1831. Once matters had been formalised by the signing of the Treaty of London in July 1840, the allies assembled an expeditionary force which achieved significant successes during September and October, followed by the naval bombardment and consequent fall of the coastal fortress of Acre on 3 November. This was carried out by a combined Anglo-Austrian fleet which included the ships-of-the-line Benbow, Bellerophon and Princess Charlotte (Admiral Stopford's flagship) as well as several of the new paddle frigates recently built for the Royal Navy. Apart from the obvious success of the bombardment, the event proved more notable for the fact that it was the very first occasion on which steam-powered ships were used in action, naval warfare being fundamentally changed thereafter.