by the time of the act of union, the kingdom of scotland had a standing army of seven units of infantry, two of horse and one troop of horse guards, besides varying levels of fortress artillery in the garrison castles of edinburgh, dumbarton, and stirling. their role was of such importance that the scots parliament forced queen anne to give royal assent to the controversial 1704 act of security by threatening to withdraw scottish forces back out of the confederate armies. the new british army created by the act of union in 1707 incorporated existing scottish regiments, such as the scots guards, the royal scots 1st of foot, king's own scottish borderers 25th of foot, the cameronians 26th of foot, scots greys and the royal scots fusiliers 21st of foot. the new armed forces were controlled by the war office and admiralty from london. during this period, scottish soldiers and sailors were instrumental in supporting the expansion of the british empire and became involved in international conflicts, including the war of the spanish succession (1702–13), the quadruple alliance (1718–20), wars with spain (1727–29) and (1738–48) and the war of the austrian succession (1740–48). the first official highland regiment to be raised for the british army was the black watch, the 43rd (later 42nd) regiment, in 1740. it marked the beginning of a major role for highlanders within the british military structure, but the growth of highland regiments was delayed by the 1745 jacobite rebellion and would not begin in earnest until the late 1750s.