Background
He was the eldest son of Frederick II, Duke of Saxe-Gotha-Altenburg and Magdalene Augusta of Anhalt-Zerbst. After the death of his father, in 1732, Frederick III assumed the duchy of Saxe-Gotha-Altenburg.
He was the eldest son of Frederick II, Duke of Saxe-Gotha-Altenburg and Magdalene Augusta of Anhalt-Zerbst. After the death of his father, in 1732, Frederick III assumed the duchy of Saxe-Gotha-Altenburg.
In 1734 he began a flourishing soldier trade with the Emperor, to the Prince of Waldeck and to the King of Prussia, which put him into the position to create a tax in his own duchy. The duchy had to suffer for Frederick with difficulty in the Seven Years" War and he forced the duchy into a war with his neighbour, duke Anton Ulrich of Saxe-Meiningen (The "Wasunger War"). They had nine children:
Frederick Louis, Hereditary Prince of Saxe-Gotha-Altenburg (b Gotha, 20 January 1735 – d Gotha, 9 June 1756).
Louis (b Gotha, 25 October 1735 – d Gotha, 26 October 1735). stillborn son (Gotha, 25 October 1735), twin of Louis. stillborn twin sons (1739).
Fredericka Louise (b Gotha, 30 January 1741 – d Gotha, 5 February 1776). Ernest II, Duke of Saxe-Gotha-Altenburg (b Gotha, 30 January 1745 – d Gotha, 20 April 1804).
Sophie (b Gotha, 9 March 1746 – d Gotha, 30 March 1746). August (b Gotha, 14 August 1747 – d Gotha, 28 September 1806).
From 1748 to 1755 he was regent of the duchy of Saxe-Weimar-Eisenach on behalf of Ernst August II Konstantin.
From 1750, he acted as regent alongside his kinsmen Franz Josias, Duke of Saxe-Coburg-Saalfeld.