In response to the annexation, the Thirty-Three Orientals, led by Juan Antonio Lavalleja, declared independence on 25 August 1825 supported by the United Provinces of the Río de la Plata (present-day Argentina). Neither side gained the upper hand and in 1828 the Treaty of Montevideo, fostered by the United Kingdom through the diplomatic efforts of Viscount John Ponsonby, gave birth to Uruguay as an independent state.
The nation's first constitution was adopted on 18 July 1830.
In 1865, the Triple Alliance was formed by the emperor of Brazil, the president of Argentina, and the Colorado general Venancio Flores, the Uruguayan head of government whom they both had helped to gain power.
The Triple Alliance declared war on the Paraguayan leader Francisco Solano López and the resulting Paraguayan War ended with the invasion of Paraguay and its defeat by the armies of the three countries.
), is a sovereign state in the southeastern region of South America.
It borders Argentina to its west and Brazil to its north and east, with the Río de la Plata (River of Silver) to the south and the Atlantic Ocean to the southeast.
Modern Uruguay is a democratic constitutional republic, with a president who serves as both head of state and head of government.
The siege of Montevideo was lifted and the Guerra Grande finally came to an end.Uruguay was inhabited by the Charrúa people for approximately 4,000 years before the Portuguese established Colonia del Sacramento, one of the oldest European settlements in the region, in 1680.Montevideo was founded as a military stronghold by the Spanish in the early 18th century, signifying the competing claims over the region.On 15 June 1838, an army led by the Colorado leader Rivera overthrew President Oribe, who fled to Argentina.In 1845, Britain and France intervened against Rosas to restore commerce to normal levels in the region.