large scale expansion began with the tensions in 1739 that led to the War of Jenkins' Ear and the War of the Austrian Succession, with five merchants being converted in June, and another eight in October. In common with the earlier vessels they were mostly employed as sloops, with only two being expended as fireships. Most were disposed of by 1745, and were replaced by further merchant vessels acquired in 1744 and 1745, and the conversion of some existing sloops and frigates. Re-rated frigates Garland (between 1716 and 1721) (between 1716 and 1718) (between 1719 and 1737) (between 1727 and 1729) (between 1734 and 1742) (between 1739 and 1743) Converted merchants (1739) Converted merchants (1744) Ex-French prizes (1745–1746) (intended for conversion but captured by a privateer before it could take place) Converted sloops (1746) Converted sixth rate (1747) Seven Years' War (1756–1763) There were no fireships in service by the early 1750s, but the outbreak of the Seven Years' War led to the purchase of three merchant vessels in 1756, with six more acquired by early 1757. A seventh was added in 1760, while four existing navy sloops were converted between 1758 and 1762. Converted merchants (1756–1760) Converted warships (1755–1762) Lightning (converted in 1755) (converted in 1758) (converted in 1758) (converted in 1762) Purchased vessels (1771) The Admiralty initially intended to purchase three vessels to be converted to fireships. Only two were purchased, but neither was converted. Both instead entered service as ship sloops under different names. (later Scorpion) (later Raven) American War of Independence (1775–1783) The outbreak of war with the American colonies in 1775 led to the purchase of a range of merchant vessels for conversion, though most spent their careers employed as sloops. These were supplemented by the conversion of twelve existing navy sloops. A significant development during this period was the reintroduction of purpose-built fireships to the navy, the first for seventy years. The Tisiphone class was introduced during the later stages of the war, and all of the vessels of the class were still in service by the outbreak of the French Revolutionary Wars a decade later, though most had served as sloops, or been officially re-rated as sloops at some point in their careers. Purpose-built Tisiphone class (1781) Purchased vessels (1777–1782) Converted warships (1775–1779) Strombolo (converted in 1775) Pluto (converted in 1777) Firebrand (converted in 1778) Salamander (converted in 1778) (converted in 1779) (converted