Sophia Frederika-Augusta, later known as Catherine, was born on May 2, 1729 in the Baltic port city of Stettin, then part of German Pomerania. She was born into the Anhalt-Zerbst family, one of the poorest and darkest German princely families. Her father, Christian Augusta, did not become the reigning prince of Zerbst until Catherine was thirteen. In 1743, at the age of fifteen, Catherine's mother Johanna found her husband. She was to marry Grand Duke Peter III of Holstein, she was sixteen years old. When Catherine met her husband, she thought he was weak, selfish, unbalanced, ineffectual, and entirely Lutheran and German in his attitude. Catherine decided to convert to Russian Orthodoxy after a year of education and training at the Russian court. She married in 1745 and became Grand Duchess Catherine of Russia. Catherine's life as Grand Duchess from 1745 to 1762 was very difficult. Their marriage was never on good terms. Catherine thought she should make her own way and find her place within the Russian court. He learned to speak Russian to convince the court of his goodwill. She studied the rituals of Orthodoxy and was careful to show respect for her new religion. Catherine made a point of reading everything she could find. She particularly liked the works of Plato and Voltaire. Her interest in intellectual things caused an even greater distance between her and Pietro. Many years passed and there was still no heir to the throne. Empress Elizabeth of Russia, Peter III's aunt, was irritated because she wanted to secure a powerful dynasty and could not do so without the presence of a male heir. She thought it was Catherine's fault because she wasn't attracted to her husband. However, it was Peter who was unable to father a son, so Elizabeth permitted an affair between Catherine and a Russian military officer named Serge Saltykov. Catherine finally gave birth to a son, whom the Empress named Paul, on 20 September 1754. Peter accepted him as his own. Soon after Paolo's birth, Elizabeth took him into her apartment and raised him as her own. This caused the relationship between Pietro and Caterina to grow further apart. On Christmas Day 1761 Empress Elizabeth Petrovna died and the reign of Tsar Peter