Alongside Maria Theresa and Frederick the Great, this ruler participated in the Partitions of Poland, and was friends with writers like Diderot and Voltaire.
This ruler's army defeated the forces of Mandalzade Hüsameddin at the Battle of Chesme, which resulted in Wallachia and Moldavia being given back to the Ottomans in the treaty of Kucuk-Kaynarca. This ruler helped place Stanislaw Poniatowski on the throne of Poland, and faced a Cossack rebellion led by Yemelyan (*) Pugachev. Alongside Maria Theresa and Frederick the Great, this ruler participated in the Partitions of Poland, and was friends with writers like Diderot and Voltaire. This successor to Peter III  was assisted by men such as Grigory Orlov and Grigory Potemkin, her lover. For ten points, identify this longest-serving Russian empress.
This ruler's army defeated the forces of Mandalzade Hüsameddin at the Battle of Chesme, which resulted in Wallachia and Moldavia being given back to the Ottomans in the treaty of Kucuk-Kaynarca.
{Catherine the Great} (accept {Catherine II} or {Yekaterina II} Velikaya or {Yekaterina Alexeevna}; prompt on Catherine)