In 1761, after the death of the Empress Elizabeth, when a war seemed imminent between Russia and Denmark, Rantzau, who wished to be on the stronger side, went to St. Petersburg and offered his services to Peter III., as a Holstein nobleman who owed allegiance to Russia rather than to Denmark. But even the sottish Tsar knew what manner of man the Holsteiner was, and rejected his offer with contumely. In revenge, Rantzau went over to Catherine and the Orloffs, and was involved in the conspiracy which resulted in the deposition and assassination of Peter III. When Catherine the Great was firmly seated upon the Russian throne she had no further need of Rantzau, and instead of rewarding him, ignored him. Rantzau therefore left St. Petersburg and returned to Holstein, a sworn foe of the Empress and eager for revenge on her. It was during this sojourn in Holstein that his acquaintance with Struensee began, and, as at this time Rantzau could get no help from his father, Struensee is said to have lent him money to go to Copenhagen, whither he went to regain his lost favour at the Danish court. In this he was foiled by the influence of the Russian envoy Filosofow, who was then all-powerful, and Rantzau was forced to return again to Holstein, where he remained until his father's death in 1769--the year before the King and Queen came to Holstein on their tour. Rantzau should now have been a rich man, for in addition to the property he inherited from his father, he had married an heiress, the daughter of his uncle, Count Rantzau Oppendorft, by which marriage the estates of the two branches of the family were united. But Rantzau was crippled with debt, and on succeeding to his inheritance he continued to live a reckless, dissipated life, and indulged in great extravagance. On the other hand, he was a good landlord to his people, and they did whatever he wished. On account of his ancient name, vast estates and the devotion of his peasantry, Rantzau had much influence in Holstein, which he persistently used against Russia.