Following years of negotiation, three Great Powers, Russia, the United Kingdom and France had come to agree to the formation of an autonomous Greek state under Ottoman suzerainty, as stipulated in the Treaty of London. Ottoman refusal to accept these terms led to the Battle of Navarino, which effectively secured complete Greek independence. That year, the Third National Assembly at Troezen established the First Hellenic Republic. With the help of a French expeditionary force, the Greeks drove the Turks out of the Peloponnese and proceeded to the captured part of Central Greece by 1828. As a result of years of negotiation, Greece was finally recognized as an independent nation in May 1832.