Rosas suspected that Santa Cruz was using the Unitarians, in alliance with Uruguayan President Fructuoso Rivera, to seize the provinces of northwestern Argentina, since it had already done so in Peru.

In September 1836, the Chilean confidential agent Francisco Javier Rosales showed Rosas documents in this regard, which confirmed the rumors that the unitary Juan Galo Lavalle was in negotiations with Santa Cruz to establish a state between Argentina and Bolivia.

[7] Persuaded by the minister Diego Portales, José Joaquín Prieto declared war on November 11, 1836, with the northern Peruvians opposed to Santa Cruz and its confederation.

Such an important acquisition must be at work with the exclusion of the Salteños and Jujeños[9] On February 13, 1837, there was a border incident when a Bolivian party entered Argentine territory in the Cochinoca area in search of Colonel José Cáceres, who was recruiting soldiers and they arrested him.

[11] Santa Cruz had appointed Otto Philipp Braun as commander of operations in the south, seconded by Generals Francisco Burdett O'Connor, Sebastián Ágreda and Timoteo Raña.

On February 14, 1839, General Velasco, the new president of Bolivia, informed the governor of Jujuy of the end of the state of war and showed himself willing to negotiate the problem of Tarija.

On April 26, 1839, General Rosas officially put an end to the war without taking advantage of the defeat of Santa Cruz to advance on Tarija, allowing them to decide the issue.