At the start of the decade, most of Greece was under the rule of the Ottoman Empire, as it had been since 1453, despite frequent revolts. In early 1821, a secret organization called the Filiki Eteria instigated several battles that, together with the blessing of a Greek flag and proclamation of uprising by Bishop Germanos of Patras on March 25, marked the beginning of the revolution. The uprising successfully established a foothold in the Peloponnese, seizing Tripolitsa in September 1821, and had some success in Crete, Macedonia and Central Greece.