This first naval action was actually fought under the Spanish flag. When Buenos Aires declared Independence from Spain in May 1810, Paraguay remained first loyal to Spain and King Ferdinand VII, who was then imprisoned by Napoleon in France. In order to force Asuncion to join the revolution, eight Paraguayan merchant vessels were seized at the river port of Corrientes by D. Elias Galvan. The Paraguayans organised a flotilla of four ships with 210 men, as follows; a fourth ship x 44 men, the flagship "NUESTRA SENORA DEL ROSARIO" commanded by José Doldan, with 6 guns and 77 men, this ship was identical to the "COMANDANTA".

While a polacra "VIZCAINA" with 3 guns and 72 men was like the "ALMIRANTA" was commanded by Miguel Felíu, the "LA PERUANA" was a gunboat with one gun and 17 men commanded by Lieutenant Martin Fleitas, and the fourth was a goletta with 2 guns and 44 men. The "LA PERUANA" had been sunk earlier by accident, but was re-floated by the Paraguayans. These ships were under the overall command of LT. Colonel José Antonio de Zavala y Delgadillo, the flotilla left Asuncion at 4 p.m. on the 21st September 1810 and reached Corrientes on the 1st October. Under the threat of the assembled Royalist flotilla the local authorities agreed to all demands without a fight. The Paraguayans left after 24 hours and were back in Asuncion 19 days after they had left. It is possible that the fourth ship was named "MINONES" commanded by Juan José Machain.