The Tarija War (Spanish: Guerra por Tarija), also known as the War between Argentina and the Peru–Bolivian Confederation (Spanish: Guerra entre Argentina y la Confederación Perú-Boliviana), was an armed conflict that occurred between 1837 and 1839. Because it happened while the Peru–Bolivian Confederation was engaged in a parallel war against the Republic of Chile during the so-called War of the Confederation, both conflicts are often confused. The Tarija War began on May 19, 1837, when Juan Manuel de Rosas, who was in charge of managing foreign relations for the Argentine Confederation and was governor of the Province of Buenos Aires, declared war directly on President Andres de Santa Cruz because of the Tarija Question and Confederation's 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. The war continued 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 engagements, the most important of which was the Battle of Montenegro, which in practice led to Argentina's withdrawal from the war, which from then on had a defensive posture being maintained, but 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.
