Alexander was sent to the Tsaritsyn Line in 1731. During the War of the Polish Succession in 1733, he was put in command of a newly-formed special regiment. In 1736 he fought in the Russo-Turkish War (1735-1739) and was present in Burkhard Christoph von Münnich's Crimean campaign and the battle at the Solyan lake under the command of Lieutenant General Izmailov. On 9 December 1736 Bruce was promoted to colonel and put in command of the Reval Dragoon Regiment and the following year he was present at the siege of Ochakov. He fought in the 1738 Dniester campaign and the 1739 Moldavian campaign, taking part in the capture of Khotin. On 14 February 1740, after the war's end, he was promoted to major general. For a short time from 29 March 1740 he was also vice-governor of Moscow.