Frederick Augustus was born in Dresden; December 23, 1750. Saxony became a kingdom (December 11, 1806) following the dissolution of the Holy Roman Empire under Napoleon's Confederation of the Rhine (July 12, 1806). The confederation was formed after Napoleon defeated the forces of the Holy Roman Emperor Francis II at the Battle of Austerlitz. Frederick Augustus thus served as Elector of Saxony, as part of the HRE, and King of Saxony under the Rhine Confederation.
Scott covers Frederick Augustus in his "Life of Napoleon Buonaparte". The Battle of Leipzig (October 16-19, 1813) in Saxony proved very costly to Napoleon. Though he ultimately prevailed over German forces, this battle was a prelude to his abdication and exile in Elba. Per Scott, Napoleon appreciated Frederick's character:
"...Perhaps also, Napoleon might be influenced by the feeling of what was due to the confidence and fidelity of Frederick Augustus of Saxony, who, having been so long the faithful follower of his fortunes, was now to be abandoned to his own. To have set fire to that unhappy monarch's city, when leaving him behind to make terms for himself as he could, would have been an evil requital for all he had done and suffered in the cause of France..."