The certainty of war between his Catholic Majesty and Portugal, being received at Rio Grande St. Pedro, in June, 1801, the governor immediately ordered a proclamation to be issued to the corps de guard, to regard the Spanish nation as enemies; and, in the expectation of an order coming from the capital to make a formal declaration, he pardoned all deserters who were willing to take up arms. An official letter now arriving from his excellency the Viceroy, the campaign commenced by the marching of troops in two bodies to the frontier of Rio Pardo and Rio Grande. By the narrow land between the lake Mirim and the ocean, S. Soares and J. Antunes marched with one hundred and fifty men against the camp of Chuy, which was surprised, sacked, and abandoned, without any loss on the part of the assailants. This corps passed to the other side of Rio de St. Gonçalo, and halted at Herval, in front of some advanced posts established on the north of the Jaguaron, which the Spaniards abandoning, the Portuguese demolished. The same misfortune befel all the other Spanish detachments, as far as the vicinity of the Jacuhy, without excepting fort St. Teela. On the Spanish guards retiring towards the post of Cerro-largo, twelve leagues to the south of the Jaguaron, on the Batuvi, they had a re-encounter with a party of Portuguese, who put them to flight, took six waggons with ammunition, provisions, and mathematical instruments. A small party of the Portuguese and Spaniards engaged each other on the Jaguaron, when the former were successful, returning with fifty prisoners, having lost only two men. Shortly after, a colonel passed to the other side of the river with twelve hundred Portuguese, and marched to the attack of the Spanish fort at Cerro-largo. Before the Portuguese had fired many guns, some cartridges of powder took fire, and a horse taking fright threw the cavalry into disorder, which spread through the whole detachment. Animated by this event, and wishing to take advantage of it, a sortie was made by a squadron of Spanish cavalry; but the Portuguese forming again, they were obliged to retreat. This trifling reverse, and the smallness of the garrison, induced the commandant to capitulate. The Portuguese apprehending, however, the arrival of some Spanish reinforcements from Monte Video, dismantled the fort and returned to their former position. Shortly afterwards, the large reinforcement which left Monte Video in order to succour the pass of Cerro-largo, arrived at the opposite banks of the river. The Portuguese showing at the same time a resolute determination to oppose their passage. In this state of things, the news of peace arrived and terminated the campaign.