Battle of Valmy
During the War of the First Coalition against France, the Prussian and Austrian troops that had invaded France retreated after the Battle of Valmy, allowing the French revolutionary army to counterattack. The troops of General Custine entered the Palatinate in late September and occupied Mainz on 21 October 1792. The ruler of Mainz, Elector-Archbishop Friedrich Karl Joseph von Erthal, had fled the city.