War is war, and as brutal as los Norte Americanos may have been, do not think for a second that the Mexicans were any less so. Nor were los San Patricios. As for their motives, at best they were mixed. As others have said, the Mexicans employed a strategy of what we would now call psychological warfare, and they did whatever they could to turn the Ameriacns against each other and to encouage desertion. They particularly targeted Roman Catholics and/or recent immigrants to the USA, who at the time were victims of Know-Nothingism and Protestant Nativism. That a few deserted is not surprising, but the reality is that the overwhelming majority saw the Mexican propaganda for what it was. Among los San Patricios themselves, there were varied reasons for doing what they did. Some may have been truly motivated by good intentions. Others were fugitives, renegades, thieves, and the like, who saw this as a chance to escape court-martial and a likely noose. Others were merely adventures and freebooters who couldn't resist a good fray. And I am certain that some where just closed minded religious bigots who were easily seduced by images of saints waved in front of their eyes.

--- Steve