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 most obscure of all German princely families. Her father, Christian Augusta, did not become 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, he was sixteen years old. When Catherine met her husband, she found him weak, selfish, unbalanced, ineffective and entirely Lutheran and German in his attitude. Catherine decided to convert to Russian Orthodoxy after a year of instruction and education 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 believed that she would have to chart her own course and find her place within the Russian court. She learned to speak Russian to convince the court of her good will. She studied the rituals of Orthodoxy and was careful to show respect for her new religion. Catherine busied herself reading everything she could find. She particularly appreciated the works of Plato and Voltaire. Her interest in intellectual things created an even greater distance between her and Peter. Many years passed and there was still no heir to the throne. Empress Elisabeth of Russia, aunt of Peter III, was irritated because she wanted to secure a powerful dynasty and could not achieve this without the presence of a male heir. She thought it was Catherine's fault because she was not attracted to her husband. However, it was Peter who was unable to produce a male 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 September 20, 1754. Peter accepted him as his own. Immediately after Paul's birth, Elizabeth took him into her apartment and raised him as her own. This caused Pierre and Catherine's relationship to grow further apart. On Christmas Day 1761, Empress Elizabeth Petrovna died and the reign of Tsar Peter