The War between Argentina and Peru–Bolivian Confederation was an armed conflict that occurred between 1837 and 1839. Because it happened simultaneously when the Peru–Bolivian confederation was engaged in a parallel war against the Republic of Chile, in the so-called War of the Confederation, the first conflict referred here is often confused with the second. The war began on May 19, 1837, when the then in charge of managing foreign relations for the Argentine Confederation and governor of the Province of Buenos Aires, Juan Manuel de Rosas, declared war directly on President Andres de Santa Cruz, both for the Question of Tarija and its support for the Unitarian Party. The operations began in August 1837 when Bolivian confederate troops invaded most of the Province of Jujuy, the Puna de Jujuy and the north of the Province of Salta. Continuing with a series of combats and skirmishes between both forces, all of them without conclusive results. In May and June 1838, the Confederate army defeated Rosas's troops in a series of encounters, the most important of which was the Combate de Montenegro or Combate de la Cuesta de Coyambuyo, which in practice led to the Argentine withdrawal from the war that from then on he maintained a defensive posture, although the state of war continued until the victory of the Chilean-Peruvian restorative army at the Battle of Yungay, which put an end to the Peru-Bolivian Confederation. The question of the Unitarian Party Relations between the Peru-Bolivian Confederation and the Argentine Confederation had deteriorated, among other reasons due to Bolivian President Andrés de Santa Cruz's support for members of the Unitarian Party that carried out at least four incursions from southern Bolivia to the northern Argentine provinces in the years before the war. One of them was that of Colonel Javier López in 1834, which culminated in his defeat in the Battle of Chiflón. A new attempt by López in 1835 was defeated at the Battle of Monte Grande, where he was shot. Also in 1835 Felipe Figueroa invaded the Province of Catamarca and in 1836 Mariano Vázquez, counting Bolivian forces among his ranks, attacked towns in Puno In August 1835, Argentine forces entered Bolivian territory to arrest José Antonio Reinafé and Cornelio Moyano, which exacerbated border tensions. 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