Preobrazhensky Regiment and the ambassadors of France and Sweden. Ivan VI and his parents died in prison many years later. House of Holstein-Gottorp-Romanov The Holstein-Gottorps of Russia retained the Romanov surname, emphasizing their matrilineal descent from Peter the Great, through Anna Petrovna (Peter I's elder daughter by his second wife). In 1742, Empress Elizabeth of Russia brought Anna's son, her nephew Peter of Holstein-Gottorp, to St. Petersburg and proclaimed him her heir. In time, she married him off to a German princess, Sophia of Anhalt-Zerbst. In 1762, shortly after the death of Empress Elizabeth, Sophia, who had taken the Russian name Catherine upon her marriage, overthrew her unpopular husband, with the aid of her lover, Grigory Orlov. She reigned as Catherine the Great. Catherine's son, Paul I, who succeeded his mother in 1796, was particularly proud to be a great-grandson of Peter the Great, although his mother's memoirs arguably insinuate that Paul's natural father was, in fact, her lover Sergei Saltykov, rather than her husband, Peter. Painfully aware of the hazards resulting from battles of succession, Paul decreed house laws for the Romanovs – the so-called Pauline Laws, among the strictest in Europe – which established semi-Salic primogeniture as the rule of succession to the throne, requiring Orthodox faith for the monarch and dynasts, and for the consorts of the monarchs and their near heirs. Later, Alexander I, responding to the 1820 morganatic marriage of his brother and heir, added the requirement that consorts of all Russian dynasts in the male line had to be of equal birth (i.e., born to a royal or sovereign dynasty). Age of Autocracy Paul I was murdered in his palace in Saint Petersburg in 1801. Alexander, I succeeded him on the throne and later died without leaving a son. His brother, crowned Nicholas I, succeeded him on the throne in 1825. The succession was far from smooth, however, as hundreds of troops took the oath of allegiance to Nicholas's elder brother, Constantine Pavlovich who, unbeknownst to them, had renounced his claim to the throne in 1822, following his marriage. The confusion, combined with opposition to Nicholas' accession, led to the Decembrist revolt. Nicholas I fathered four sons, educating them for the prospect of ruling Russia and for military careers, from whom the last branches of the dynasty descended. Alexander II, son of Nicholas I, became the next Russian emperor in 1855, in the midst