A Brief (ish) history of Cathrine the Great, Empress of Russia-
Sophie Friederike Auguste von Anhalt-Zerbst was born on 2 May 1729 in Stettin, then part of Prussia (now Szczecin in Poland), the daughter of a minor German prince. In 1745, after being received into the Russian Orthodox Church, and changing her name to Catherine, she married Grand Duke Peter, grandson of Peter the Great and heir to the Russian throne.
The marriage was unhappy, but the couple did produce one son, Paul. In 1762 Catherine's husband became Tsar Peter III but he was soon overthrown with Catherine being declared empress. Peter was then killed shortly afterwards and it is not known whether Catherine had a part in his death. She subsequently had a series of lovers whom she promoted to high office, the most famous and successful of whom was Grigori Potemkin.
Catherine's major influences on her adopted country were in expanding Russia's borders and continuing the process of Westernisation begun by Peter the Great. During her reign she extended the Russian empire southwards and westwards, adding territories which included the Crimea, Belarus and Lithuania. Agreements with Prussia and Austria led to three partitions of Poland, in 1772, 1793, and 1795, extending Russia's borders well into central Europe.
Catherine began as a political and social reformer but gradually grew more conservative as she got older. In 1767 she convened the Legislative Commission to codify Russia's laws and in the process modernised Russian life. She presented the commission with her Nakaz, (or 'Instruction'), a strikingly liberal document that presented the empress’s vision of the ideal government. The commission produced no desired results and the outbreak of war against the Ottoman Empire in 1768 provided a good opportunity to disband it.
The Pugachev Rebellion of 1774-1775 gained huge support in Russia's western territories until it was extinguished by the Russian army. Catherine realised her heavy reliance on the nobility to control the country and instigated a series of reforms giving them greater control over their land and serfs. *continued in comments*