The Catholic Defender: President James K. Polk introduced the first official Catholic priests to serve as U.S. military chaplains.

President James K. Polk prompted the U.S. Congress declares war on Mexico | May 13, 1846 after a disputed border clash on the Rio Grande, and indeed introduced the first official Catholic priests as U.S. military chaplains.

 Polk sent Zachary Taylor's troops into disputed territory, leading to Mexican fire and casualties that Polk used to claim "American blood was shed on American soil"

 A large minority of U.S. soldiers—especially Irish and German immigrants—were Catholic.

Polk and commanders wanted to prevent Mexico from framing the invasion as an anti-Catholic religious crusade and to stop Catholic U.S. soldiers from feeling conflicted or fraternizing with local churches.

 President Polk and Secretary of War worked with New York Archbishop John Hughes to select Jesuit priests.

 Fathers John McElroy and Anthony Rey joined General Zachary Taylor's army at Matamoros in July 1846.

 Before 1846, official U.S. military chaplaincies were exclusively Protestant.

Father Anthony Rey met a tragic end, becoming the first Catholic chaplain killed during service with the United States military. 

Appointed as an Army chaplain by President James K. Polk in May 1846, the French-born Jesuit priest was assigned to General Zachary Taylor's army. He served alongside his colleague, Father John McElroy.

Father Rey was highly praised by both Catholic and Protestant soldiers for his exceptional courage during the Battle of Monterrey (September 21–24, 1846). Instead of remaining safely in the rear, he went directly into active urban combat to treat the wounded, offer comfort, and administer last rites to the dying. Following the capture of the city, he remained in the area and quickly learned Spanish so he could minister to local Mexican rancheros.

In January 1847, determined to continue his outreach, Father Rey set out toward Matamoros to visit Father McElroy. U.S. military officers strongly advised against the journey due to rampant guerrilla warfare and regional instability.

On January 19, 1847, after preaching to a mixed congregation of Americans and Mexicans in the village of Ceralvo, Father Rey and a young Irish assistant went missing. A few days later, his body was discovered nearby. He had been pierced with lances and murdered, a crime historical consensus attributes to a band of localized roadside thieves or guerrilla bandits, potentially led by the regional chieftain Antonio Canales Rosillo.

Though it is documented that he was buried in Mexico, the exact location of his grave remains unknown.

Prior to his deployment, the broader Protestant establishment and nativist press had viewed the appointment of Catholic chaplains by President James Polk with severe suspicion, often framing it as a "papist conspiracy". However, following his murder by Mexican guerrillas, the public and media narrative shifted through two distinct lenses.

 Catholic newspaper editors aggressively utilized Father Rey's death to repudiate anti-Catholic propaganda and counter nativist bigotry. They pointed to his sacrifice as the ultimate, irrefutable evidence that Catholics and adopted citizens were deeply loyal to the United States.

The Catholic press highlighted his and fellow chaplain Father John McElroy's compassionate service, emphasizing that they provided medical and spiritual care to soldiers of all faiths without prejudice.

 Within the military itself, his death was widely mourned as a significant blow by both Catholic and Protestant U.S. soldiers who had served alongside him.