The Colorados favored the exiled Argentine liberal Unitarios, many of whom had taken refuge in Montevideo while the Blanco president Manuel Oribe was a close friend of the Argentine ruler Manuel de Rosas. On 15 June 1838, an army led by the Colorado leader Rivera overthrew President Oribe, who fled to Argentina. Rivera declared war on Rosas in 1839. The conflict would last 13 years and become known as the Guerra Grande (the Great War).