His baptism of fire took place in the battle of Cerrito, on New Year's Eve, 1812, during the Second Siege of Montevideo, a feat of arms that ended in a victory for the Patriots.

The personal rivalry between Rivera and Oribe, which apparently dates from such events, the young officer decided to abandon his boss.

Carlos Federico Lecor, commander of the occupying forces, offered no hindrance to the passage of eastern officials in Buenos Aires, even though he could not attract them to your cause.

In Buenos Aires, known by the certifying of stationery at the time, since 1819, Oribe, along with other Orientals as Santiago Vazquez and residents who were equally opposed to the Brazilian Portuguese occupation and Artigas, have built a secret Masonic society, called the Society of the Eastern Knights, who waited at least until 1821, Cisplatin Congress to undertake a return to the, since then, called Cisplatina Province and begin work to reverse the situation.

At last Oribe was defeated in 1851 with help from Brazil and Argentine rebels, led by Justo José de Urquiza, who were against Rosas.