John Pinheiro’s Missionaries of Republicanism is, according to the subtitle, a “religious history of the Mexican-American War.” He shows how the war was infused with religious themes, linking American Protestantism with Anglo-Saxonism and Manifest Destiny. Near the heart of the religious justification of the war was anti-Catholicism: The United States could fulfill its world-historical role only by fending off the internal threat of Irish Catholic immigration and the external threat of Catholic Mexico.

As Pinhiero summarizes the anti-Catholic sentiment: “If Roman Catholicism was inimical to republican government, and if the foundation of republicanism lay in Protestant Christianity and its hermeneutics, then Americans had a duty to oppose the former and strengthen the latter in order to keep their country free.”

That is, they had to suppress Catholicism to preserve the particular form of religious liberty for which American was famed: Suppressing Catholicism “might be the chief of those obligations on the other side of the coin from liberty. This real, felt sense of duty might seem far-fetched, easily getting lost amid the strident religious bigotry, conspiratorial nonsense, and incendiary language of the anti-Catholic movement. Yet to oppose the one particular religion that promised to squelch all others and weaken Americans’ hard-won civil liberties seemed perfectly consistent with the principle of religious freedom and not at all hypocritical to a growing number of Americans by the mi-1830s. That is, limiting the freedom of Catholics, especially those recently arrived from a European monarchy with no experience of self-government, actually ensured religious freedom, and in doing so it preserved civil liberties as well. The truth of this paradox was seemed as sensible and as uncontroversial as confining criminals to jail in order to protect the community from further crime” (26).

Because “Catholic paid homage to a foreign potentate whom Protestants identified with the anti-Christ, were controlled like so many marionettes by their bishops, and slavishly obeyed orders given by priests in the ark of confessionals,” they threatened to “enervate the one nation here the true gospel went hand-in-hand with civil and religious liberty and where all humanity looked for help to usher in the millennial reign of Jesus Christ.” For American Protestants, “the stakes could not be higher” (27-28).

The war took on the character of a religious crusade, an effort to convert inferior Mexican Catholics to superior Anglo-Saxon Protestantism. And the war reenforced anti-Catholic sentiment, as soldiers wrote back accounts of their first-hand encounters with Mexican Catholicism, sometimes comparing them “to Canaanites who had to be removed to make way for God’s favored people” (13).

Protestants have not universally defined themselves over-against Catholicism, but it has been done by some Protestants at some times, with ugly and tragic consequence.