A secret society, the "Society of Friends", was founded in Odesa, Russia's largest port in the Black Sea by Emmanuel Xanthos from Patmos, Athanasios Tsakalov from Giannena and Nikolaos Skoufas from Arta. Its goal was to liberate the Greeks from the Ottoman rule. Like the masonic societies of the time, it had a concealed nature, ritualistic initiation procedures, complex internal hierarchy, and strict regulations for self-protection. In 1818 the society's headquarters were transferred to Istanbul. Emmanuel Xanthos offered the leadership of the society to the Minister of the Russian Tsar Ioannis Kapodistrias, but he declined it. Finally, in 1820, the Tsar's aide, Alexandros Ypsilantis, a descendant of one of the most influential Phanariot families, took over the society's leadership. He was the person who declared the beginning of the Revolution in February 1821 with the crossing of the Prut river.