The naval Battle of Juncal took place between a squadron of the newly independent United Provinces of the River Plate under command of William Brown and a squadron belonging to the Brazilian Empire, commanded by Sena Pereira. It spanned two days, from 8 to 9 February 1827, in the waters of the Río de la Plata. The two squadrons were initially of roughly equal strength, but because of superior command and control, and gunnery training, the Argentines scored a decisive victory: out of 17 Brazilian vessels, 12—including the flagship with its admiral—were captured and 3 were burnt. Not a single Argentine vessel was lost. In the aftermath of the battle, the Third Division, the arm of the Brazilian fleet tasked with controlling the Uruguay River and thus disrupting communications with the Argentine army then operating in the Cisplatina province, was completely destroyed. The result was the biggest naval victory for Argentina in the Cisplatine War. The situation before the battle The divisions of the imperial fleet During the second year of the Cisplatine War, the Brazilians took advantage of their numerical superiority on sea and divided their naval forces operating in the Río de la Plata sector into three squadrons, or "divisions". The first division, "Bloqueio", was placed under the command of John Charles Pritz. It was tasked with blockading traffic to and from the port of Buenos Aires and secondary departure points such as Las Conchas, Ensenada de Barragán, and the mouth of the Salado River; The second division, named "Oriental" or "Mariath", was tasked with securing the Uruguayan coast from the mouth of the Uruguay River to the Río de la Plata. The bulk of this division was put under the command of Frederico Mariath, who would later support the Third Division; The "Third Division", under the command of Jacinto Roque de Sena Pereira, was to remain in the Uruguay River in order to divide the Argentine front and exploit political fault lines between the province of Entre Ríos and Buenos Aires that had been exacerbated by the passing of the Unitary Constitution of 1826. By controlling the Uruguay River, the supply lines to an Argentine expeditionary force in the contested territory of Cisplatina (present-day Uruguay) would be cut, and the Brazilians would have freedom of maneuver for a later attack on the Argentine flank. First Argentine advance To confront the three threats, each of similar or superior