The Mission is based on events surrounding the Spanish – Portuguese treaty of 1750 or ‘Treaty of Madrid’.
The document was signed in the Spanish capital by Ferdinand VI of Spain and John V of Portugal on 13th January 1750.
Spain ceded part of Jesuit Paraguay to Portugal, to end to the armed conflict between the Spanish and Portuguese empires in South America.
The ‘Treaty of Madrid’ was significant because it substantially defined the borders between the Spanish and Portuguese empires, ceding much of what is today’s country of Brazil to the Portuguese.
However, the resistance of the Jesuits to surrendering their missions and the refusal of the Guarani to be forcibly relocated led to the nullification of the treaty. The opposition by the Guarani led to the Guarani War of 1756.
A significant subtext of the film is the impending suppression of the Jesuits, of which father Gabriel is warned by the narrator, Cardinal Altamirano, who was once himself a Jesuit.
Altamirano, speaking in hindsight in 1758, corresponds to the actual Andalusian Jesuit Father Luis Altamirano, who was sent by Jesuit Superior General Ignacio Visconti to Paraguay in 1752 to transfer territory from Spain to Portugal.
He oversaw the transfer of the Seven Missions south and east of the Río Uruguay, that had been settled by Guaraní and Jesuits in the 17th century.
As compensation, Spain promised each mission 4,000 pesos, or fewer than 1 peso for each of the circa 30,000 Guaraní of the seven missions, while the lands were estimated to be worth 7 – 16 million pesos.
The film’s climax is the Guaraní War of 1754–1756, during which historical Guaraní defended their homes against Spanish-Portuguese forces implementing the Treaty of Madrid.
For the film, a re-creation was made of one of the Seven Missions, São Miguel das Missões.
The film’s theme ‘Gabriel’s Oboe’ is most prominently used when the protagonist, the Jesuit Father Gabriel, walks up to a waterfall and starts playing his oboe.
Aiming to befriend the natives with his music so he can carry his missionary work in the New World.
The Guarani, who have been stalking him from a distance, approach Gabriel for the first time. The chief, however, is displeased by this, and breaks Gabriel’s oboe.
This marks the beginning of the relationship between Father Gabriel and the Guaraní.
The waterfall setting of the film suggests the combination of these events with the story of older missions, founded between 1610 – 1630 on the Paranapanema River above the Guaíra Falls, from which Paulista slave raids (Bandeirantes) forced Guaraní and Jesuits to flee in 1631.
The battle at the end of the film evokes the eight-day Battle of Mbororé in 1641, a battle fought on land as well as in boats on rivers, in which the Jesuit-organised, firearm-equipped Guaraní forces stopped the Paulista raiders.