During the war between France and Spain (in 1801), Francisco da Silveira, along with other important people in the province, raised a voluntary corp, and as sergeant figured in the Monterei company, commanded by Gomes Freire de Andrade.

He was in Aveiro, when in December he was called to Coimbra to testify for the annihilation of the 6th, 9th, 11th and 12th regiments, by General Junot.

With the fall of the monarchy in sight, he escaped to Porto in order to board an English ship, where he assumed that he would depart for Brazil.

His plan foiled, he escaped to Vila Real, where he later became one of the factors in the acclamation of the legitimate government in 1808.

He commanded a Portuguese division in Arthur Wellesley, Marquess of Wellington's Allied army at the Battle of Vitoria on 21 June 1813.