He was involved in diverse situations in the disputed territories between the Portuguese and Spanish in the territory that today is the South region in Brazil. He organized the support for the Sacramento Colony during the Spanish-Portuguese War, 1735-1737, and went head-to-head with his Spanish rival, Don Pedro de Ceballos Cortez y Calderón.
For the purpose of maintaining the territory in the hands of Portugal, Pais was charged with construction of the Fortress Jesus Maria e José in the town of Rio Grande. That area was the object of the Spanish incursion commanded by Pedro de Ceballos, who invaded it twice.
On Santa Catarina Island, when it was in Spanish hands under the authority of Pedro de Ceballos, the Brigadier General Pais invaded and took the island for Portugal, placing himself as governor. He remained governor of the captaincy of Santa Catarina from 1739 until 1745.
He planned the construction of forts which would constitute the defense of Santa Catarina Island: in the north, Fortaleza de São José da Ponta Grossa, Fortaleza de Santa Cruz de Anhatomirim, and Fortaleza de Santo Antônio de Ratones; and in the south: Fortaleza de Nossa Senhora da Conceição de Araçatuba.