At one time, almost no-one in South America had even heard of Jesus, an alarming fact to the Catholic church. So for hundreds of years, Dominican and Franciscan friars and eventually Jesuits were sent in to rectify the situation. 1986's The Mission tells a story of that last group of missionaries, the Jesuits, less than twenty years before their order would be dissolved by the Pope due to external political pressures. The film is partly an argument as to the nature of those pressures--essentially, capitalism--but is for the most part simply a long, beautiful commercial for Catholicism. And I sincerely mean beautiful and with great performances.
The film stars five Catholic actors--Jeremy Irons, Robert De Niro, Liam Neeson, Aidan Quinn, and Ray McAnally, the last of whom, who plays Cardinal Altamirano in the film, even trained to be a priest. All of those actors are Irish or of Irish decent (and Jeremy Irons lives in Ireland), despite the fact that all the characters they play are either Spanish or Italian (De Niro is Italian as well as Irish but he plays a Spanish character). Considering the recent fuss about Emma Stone playing a Vietnamese character, I guess this is something that probably wouldn't happen to-day. Though I'm less bothered by it in this case than I am curious. Did everyone meet in a pub in Dublin and say, hey, let's make a movie about Jesuits?
It's the kind of movie you see less often nowadays since Quentin Tarantino showed how important language is in Inglorious Basterds--where everyone speaks an English we're meant to take as Spanish. Well, everyone except the Guarani, who speak in their native tongue. This probably didn't seem strange when the movie came out and, even now, one can say that we, the English speaking audience, can understand the Europeans because its from their perspective the movie is told. But one of the problems with this movie, a problem rather reflective of the missionary attitude itself, is that, while arguing that the indigenous people of South America are people who deserve basic human rights it fails to establish any of them as people with the complex personalities of the white characters.
In fact, missionaries deliberately avoided teaching their subjects Spanish because they were worried about exposing them to other European influences, something the film doesn't mention. Instead, missionaries learned the vernacular language in order to communicate and take confession. We also see Irons' character, Father Gabriel, communicating with the music of Ennio Morricone.
Recent studies where Pygmy communities in central Africa found the soundtrack to Psycho to be jubilant suggest a flaw in the idea that refined European music is a universal language. But Ennio Morricone's score for this film is truly beautiful, if slightly overused, and pretty anachronistic coming from Gabriel's oboe.
It's not long before Gabriel encounters one of the chief obstacles in convincing the Guarani of peaceful European intentions--the mercenary Rodrigo Mendoza (De Niro) who captures members of the indigenous population to be sold as slaves. Native Americans in South America were still pressed into slavery in the mid-eighteenth century despite Bartolome de las Casas successfully advocating increased importation of slaves from Africa in order to spare the American people whom he considered more human (he later regretted encouraging the enslavement of African people). When Mendoza commits a crime he can't forgive himself for, Gabriel prescribes penance, which takes the form of Mendoza hauling his armour and weapons all the way to Gabriel's mission at the top of a waterfall.
He eventually becomes a Jesuit and helps Gabriel turn the mission into one of the idyllic, productive communities that Portuguese and Spanish authorities resent. Mendoza's skills as a mercenary come in handy when he leads the Guarani in defence of the mission once the Portuguese establish authority--though no Jesuits actually aided the Guarani in this manner in reality.
The director of the film, Roland Joffe, is agnostic according to Wikipedia but I can't find information on the screenwriter, Robert Bolt. Bolt also wrote A Man for All Seasons, a play and subsequently a film honouring Thomas More who resisted England's break with Catholicism. It's curious he would write one story about how it's important to maintain an old religion against new external influence and then another where it's taken as read than Catholicism must be imported to the Americas.