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. Between 1821 and 1824, first and second national assemblies were held, and the constitutions of 1822 and of 1823 were established. However, revolutionary activity was fragmented, resulting in the civil wars of 1824–1825. The Greek side withstood the Turkish attacks because, during this period, the Ottoman military campaigns were periodic and uncoordinated. That changed when the Ottoman Sultan Mahmud II negotiated with Mehmet Ali of Egypt, who agreed to send his son Ibrahim Pasha to Greece with an army to suppress the revolt in return for territorial gain. Ibrahim landed in the Peloponnese in February 1825 and secured most of the peninsula by the end of 1825. He then helped break the siege of Missolonghi. Although Ibrahim was defeated in Mani, he had succeeded in suppressing most of the revolt in the Peloponnese and Athens had been retaken. 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. Western Europe United Kingdom In the 1820s, the British government was formally headed by King George IV, but in practice, was led by his prime ministers Lord Liverpool (1812–1827), George Canning (1827), Lord Goderich (1827–1828), and Duke of Wellington (1828–1830). This decade was largely peaceful for Britain, with some foreign intervention. The British supported the Portuguese liberals in the Liberal Wars, and supported Greek rebels in the war for independence. During this time, London became the largest city of the world, taking the lead from Beijing. Domestic tensions ran high at the start of the decade, with the Peterloo Massacre (1819), the Cato Street