Excerpts from Books and Wikipedia
Catherine was an obscure German princess. She "won the support of her powerful mother-in-law, the Empress Elizabeth, despite the failure of her marriage to the headstrong and inexperienced Peter. She rapidly learned Russian and converted to the Orthodox Church. . . Despite seizing power in this manner, Catherine proved one of Russia's greatest rulers, expanding the empire southward to the Black Sea and enriching its prestige with an exceptional collection of art. . . . At one point, Catherine had considered freeing the serfs, but she soon saw that it was more politically expedient to tighten their bonds and the peasants' forced servitude enabled her to fund her cultural and imperial ambitions." [1001 Days]