“¡Viva Cristo Rey!” (“Long Live Christ the King.”) That was the rallying cry for millions of Mexicans during the second and third decades of the 20th century, as revolutionary governments, modeled after the Bolshevik regime in Russia, unleashed round after round of persecution and terror throughout Mexico. For Greater Glory, the newly released epic film starring Andy Garcia and Eva Longoria, provides a stirring introduction to the “Cristero War,” or “Cristiada” (1926-1929), a heroic chapter of Mexico’s history that, until now, has been almost virtually unknown in the United States (as well as in Mexico, where the government has suppressed...