Francisco Xavier de Mendonça Furtado (1701–1769) served in Portugal's armed services rising in rank from soldier to sea-captain, then became a colonial governor in Brazil and finally a secretary of state in the Portuguese government. His major achievements included the extension of Portugal's colonial settlement in South America westward along the Amazon basin and the carrying out of economic and social reforms according to policies established in Lisbon.
Childhood
Francisco Xavier de Mendonça Furtado was born in Mercês, Lisbon on 9 October 1701 and baptised on 12 October 1701 in the Chapel of our Lady of Mercy (Portuguese: Capela de Nossa Senhora das Mercês) on the Travessa das Mercês. His father was Manuel de Carvalho e Ataíde, a member of Portugal's armed forces and a genealogist, and his mother was Teresa Luisa de Mendonça e Melo.
One of twelve children, his most significant siblings were Sebastião José de Carvalho e Melo who became King José I's Secretary of State of Internal Affairs and was elevated by the king in 1769 to the title by which he is most often referred, Marquis of Pombal (Portuguese: Marquês de Pombal), and Paulo António de Carvalho e Mendonça, a member of Lisbon's clergy who became Inquisitor-General of the Inquisition for the period 1760–1770. These three brothers were closely bonded within the family (as illustrated in this painting (left)), a relationship which was further revealed in their adulthood in the way they supported each other professionally.
No information is available about Mendonça Furtado education and other activities preceding his military service apart from the record of him and his brother Paulo António de Carvalho e Mendonça being made noblemen of the royal court (Portuguese: fidalgo da Casa Real) on the same day. He was 11 years of age at that time and was using the name Francisco Xavier de Carvalho.
Speculating about his activities in early adulthood, biographer Fabiano dos Santos says, "He may have devoted himself to taking care of his family's estates … while his older brother, Sebastião José, began his diplomatic career."
Military service
On 14 April 1735 Mendonça Furtado followed his father's career and joined the armed forces where he served for 16 years rising from the rank of soldier to sea-captain.
Spanish–Portuguese War
In December the following year, he was despatched as part of a campaign to defend the Portuguese settlement of Colonia del Sacramento (, "Colony of the Holy Sacrament") from Spanish invasion in what is referred to as the Spanish–Portuguese War of 1735. The settlement established in 1680 was located on the northwestern shore of the Río de la Plata, directly opposite to the Spanish port of Buenos Aires on the river's southern shore and in the Banda Oriental ("East Bank") region, including most of modern-day Uruguay and portions of Argentina and Rio Grande do Sul and Santa Catarina in Brazil.
The war itself was predated by extensive struggles between Spain and Portugal regarding each empire's rightful ownership of South American territory. Christopher Columbus's first voyage had prompted the 1494 Treaty of Tordesillas to avoid colonial conflict but its demarcation line between the empiresnotionally 370 "leagues" west of "the Cape Verde Islands"had never been formally computed with any exactness. Even once the Spanish discovered that the agreement entitled the Portuguese to a sliver of South America, they long suffered the Brazilians to extend far beyond the line, claiming lands as far as the Amazon and Rió de la Plata estuaries, while the Habsburg monarchs were distracted by the Reformation and by wars in the Netherlands, Italy, and Balkans. The Iberian Union confused the issue further, with Spain and Portugal under a single monarch but with their subjects still jealously guarding their privileges while attempting to encroach upon the other for strategic purposes or for financial gain.
Colonia del Sacramento was west of any computation of the official meridian and therefore on Spanish territory, although Portugal argued otherwise. In any case Spain had paid little attention to the area by that time, and after the Portuguese settled there the population in and around the town expanded rapidly. It was soon producing goods and resources of value to Portugal. However, Portugal's primary motivator in settling there may not have come from commercial interests so much as its "strategic importance in resisting the Spanish."