The fort was founded in September 13 1775, something that had been planned by the Portuguese colonial authorities ever since the new borders with Spain had been fixed in the Treaty of Madrid in 1750.

Brazil's western central region, Mato Grosso, had been explored since the early 18th century by bandeirantes from São Paulo and Jesuit missionaries from land which belongs to Paraguay nowadays.

[4] In 1791, due to the bad state of the fort's structure, which had been damaged by a fire[3] and Kadiwéu attacks,[5] works were started to renew it, this time using masonry.

Then captain-general Caetano Montenegro [pt] ordered it to be built "in the edge of the hill, where two great lengths of the Paraguay River present themselves at an obtuse angle, which will be then flanked by the new fort, something the old base wouldn't do.

[8][2] In September 1801, the new fort was still being built when an expedition composed of four schooners and two canoes, carrying 600 men, attacked it; they were led by Lázaro de Ribeira [es], the intendant of Paraguay.

The fort encroached on Spanish land, as established in the Treaty of Madrid, and news of peace in the War of the Oranges hadn't yet reached the region.

[9][2] The Brazilians had been previously warned by the now friendly Kadiwéu indians of the expedition's existence,[3] and, though the fort was garrisoned by only 42 men, it resisted the initial assault and then a 10-day siege, after which the Paraguayans withdrew due to the lack of supplies and storm damage on the ships.

[8] In 1855, Mato Grosso's government was briefly transferred to the fort by then-provincial president Augusto Leverger amidst tensions with Paraguay.

Sir Commander of Arms, who returned with me that same day; I must tell Your Excellency, nevertheless, that said Fort's state is unsatisfactory, but that it can resist Paraguay's ships and maybe defend itself from land attacks.

Sir Commander of Arms has ordered some improvements and repairs be made which he understands will be advantageous, and he plans to fortify the Navy's old position in front of the Fort, so that they may fire across from each other and aid each other.

"[11][c] The Paraguayan invasion, the opening move of the Mato Grosso Campaign, was made of five infantry batallions and two dismounted cavalry regiments, totalling 3200 men, with twelve rifled guns, a French-equipped rocket battery and the support of 11 warships, all under colonel Vicente Barrios's command.