After mediation by Viscount Ponsonby, a British diplomat, Brazil and Argentina agreed to recognize an independent Uruguay as a buffer state between them. As with Paraguay, however, Uruguayan independence was not completely guaranteed, and only the Paraguayan War secured Uruguayan independence from the territorial ambitions of its larger neighbors. The Constitution of 1830 was approved in September 1829 and adopted on 18 July 1830. The "Guerra Grande", 1839–1852 Soon after achieving independence, the political scene in Uruguay became split between two new parties, both splinters of the former Thirty-Three: the conservative Blancos ("Whites") and the liberal Colorados ("Reds"). The Colorados were led by the first President Fructuoso Rivera and represented the business interests of Montevideo; the Blancos were headed by the second President Manuel Oribe, who looked after the agricultural interests of the countryside and promoted protectionism. Both parties took their informal names from the color of the armbands that their supporters wore. Initially, the Colorados wore blue, but, when it faded in the sun, they replaced it with red. The parties became associated with warring political factions in neighboring Argentina. The Colorados favored the exiled Argentinian liberal Unitarios, many of whom had taken refuge in Montevideo, while the Blanco president Manuel Oribe was a close friend of the Argentine ruler Juan Manuel de Rosas. Oribe took Rosas's side when the French navy blockaded Buenos Aires in 1838. This led the Colorados and the exiled Unitarios to seek French backing against Oribe, and, on 15 June 1838, an army, led by the Colorado leader Rivera, overthrew Oribe who fled to Argentina. The Argentinian Unitarios then formed a government-in-exile in Montevideo, and, with secret French encouragement, Rivera declared war on Rosas in 1839. The conflict would last 13 years and become known as the Guerra Grande (the Great War). In 1840, an army of exiled Unitarios attempted to invade northern Argentina from Uruguay but had little success. In 1842, the Argentinian army overran Uruguay on Oribe's behalf. They seized most of the country but failed to take the capital. The Great Siege of Montevideo, which began in February 1843, lasted nine years. The besieged Uruguayans called on resident foreigners for help. French and Italian legions were formed. The latter was led by the exiled Giuseppe Garibaldi, who was working as a mathematics teacher in Montevideo when the war broke out. Garibaldi was also made head of the Uruguayan navy. During this