Although the Russians briefly took and occupied Derbent and Baku during the expedition of 1796 under the command of count Valerian Zubov, Agha Mohammad Khan successfully expanded Iranian influence into the Caucasus, reasserting Iranian sovereignty over its former dependencies in the region. He was, however, a notoriously cruel ruler, who reduced Tbilisi to ashes, while massacring and carrying away its Christian population, much as he had done with his Muslim subjects. He based his strength on tribal manpower like Genghis Khan, Timur and Nader Shah.