Partially financed by the Knights of Columbus, whose members in both the United States and Mexico were an integral part of the actual Cristeros Rebellion.
"Joselito", the young Cristero boy played by Mauricio Kuri is based on 14 year year old St. José Luis Sánchez del Río who was put to death by the Mexican government on 10 February 1928 because he wouldn't renounce his Catholic faith. He was canonized in St. Peter's square by Pope Francis on October 16, 2016. His Feast Day is February 10th
Something not brought out in the movie, is that both Calles and Gorostieta were members of the Masons.