The San Patricios

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A great deal of antiwar literature was turning up in Matamoros, and much of it was directed at the consciences of abolitionists. Papers and religious tracts told soldiers that this was not only an unjust war but an insidious plot to spread slavery westward. In twos and threes, in squads, and in sections, about fifty men deserted, and they marched to Monterrey to put on the black shakos, the dark blue red-trimmed uniform coats, the white cross belts, and the sky blue trousers of O’Reilly’s outfit. Some of these men were motivated by religion and some by sympathy; others were adventurers drawn by the lure of land; but all were present under arms as Mexican soldiers that grim September when Taylor moved against Monterrey.

During the fighting General Ampudia often hurried to the hottest action, and inevitably he found O’Reilly and his gunners there before him. “Valientes como leones,” (“valiant as lions”) reported the general. Ampudia recommended that O’Reilly be entrusted with two brass cannon on top of the Bishop’s Palace stairs during the evening of the second day’s fighting. The Obispado was not expected to hold; U.S. troops would hit it from three sides at dawn. Positioned there were tough Mexican regulars, men who had no illusions about why O’Reilly’s men were carrying kegs of powder into the palace.

The norteamericanos attacked at first light, and they were hurled back by the regulars and the point-blank fire of O’Reilly’s guns. The Yankees came on again, and again were driven back. Throughout the fighting two Irish pioneers with lit torches waited close by fuses. The moment the position was overrun, they would send the Obispado , defenders, and attackers up in one huge, annihilating blast of black powder.

But after repelling a third assault, the forces at the palace were ordered to fall back on the plaza. They retired in good order, the sporadic skirmishing gradually dying down to leave an eerie silence over the streets of Monterrey. Taylor and Arista had worked out a cease-fire.

It lasted six weeks, time enough to give Don Antonio López de Santa Anna, the canny Mexican politician and soldier who, a decade after massacring the garrison of the Alamo, had managed to make himself known as the “Angel of Peace,” an opportunity to negotiate a peace with the United States. Taylor’s army would occupy Monterrey; Arista’s would march south with all honors of war. U.S. soldiers watched the long column depart, the veteran troops in the van, the rear made up of wives, children, camp followers, and even pets. Taylor’s men enjoyed the withdrawal as much as a circus parade until the officer commanding the rear, a magnificently mounted lieutenant, came into view. The U.S. soldiers recognized John O’Reilly; they shouted threats and curses, and, according to an officer, “the dastard’s cheek blanched.”

O’Reilly’s outfit did not stay long in bivouac. With other crack units of Arista’s army, it marched south to San Luis Potosí, where a very formidable force was mustering to be commanded by Santa Anna. Far from negotiating an end to the war, the Angel of Peace had decided to throw the norteamericanos out of Mexico.

Between 150 and 200 men were integrated into O’Reilly’s unit at San Luis. The nucleus of the force remained the U.S. deserters and occasionally a reluctant draftee.

Among the new recruits were some Irish frontiersmen from Texas who considered themselves Mexicans rather than Texans or Americans. They called their settlement San Patricio, or St. Patrick, and they may have given the name of their home to the battalion that was taking shape at San Luis.

However the outfit gained the name, it was a fitting one. More than a third of the force and all but three of the officers were Irishmen, and the unit fought under a green battle guidon that bore an image of St. Patrick. After some lobbying, O’Reilly acquired five heavy cannon, eighteen- and twentyfour-pounders. Their crews trained under Lt. Ned McHerron, formerly a sergeant of G Battery, 4th U.S. Artillery, and, as his ex-commander said, “a loyal and faithful soldier for many years in the United States Army.” A deeply religious man in his sixties, McHerron had been appalled by reports of U.S. soldiers desecrating churches at Matamoros. He made the march to Monterrey with a few comrades; one who refused to accompany him was another sergeant, his son.

McHerron became the mainstay of an uncommonly effective “flying artillery” battery. Cannon had to be protected in the field, and as late as the Civil War this could be a confusing, haphazard business of generals improvising support by taking men from battle lines and assault columns. But the support systems were built into the San Patricio Battalion from the start: outriders, two infantry companies, and sharpshooters made up of soldiers who knew their only job was to get the guns into action, maintain them, and withdraw them safely.