New York and Dublin are both well-known for their Paddy’s Day celebrations – less so Mexico City.

But el Día de San Patricio is a big day in the Mexican calendar as well.

There, the Irish tradition being celebrated isn’t music, literature, or Guinness – it’s Ireland’s proud history of internationalist solidarity against reaction.

This story goes way back.

The history of Irish Solidarity 

Irishmen, like Bernardo O’Higgins in Chile, were everywhere in the forces of Simón Bolívar and his comrades as they drove the Spanish Empire from South America at the beginning of the 19th century.

Irish volunteers (not least from New York) also played a big role in Abraham Lincoln’s Union army as it battled the slave states of the Confederacy. And, organised as the ‘Connolly Column’ (named for Easter Rising hero, James Connolly), Irishmen fought Franco’s fascist army in 1930s Spain as part of the revered International Brigades.

But in Mexico’s case, they’re celebrating another group of Irish freedom fighters – the St Patrick’s Battalion.

The San Patricios, as they were known to Mexicans, were a band of Irish immigrants to the US who had enlisted in the Yankee army which went south to invade northern Mexico in 1846.

But these guys didn’t stay in that army for long.

The Mexican-American War (1846-8) was a poorly concealed land grab by the United States against its southern neighbour.

Henry David Thoreau and other Northern progressives saw the invasion as an attempt by the Southern slavers to expand their plantation empire into Mexican lands. Thoreau was arrested for refusing to pay taxes to a federal government which would only spend them on this imperial war.

The immorality of the US invasion was not lost on the Irish troopers doing the invading.

These men didn’t only see a repulsive imperial self-interest in what they were being ordered to do in Mexico. The specifics of the case also reminded them of their suffering homeland – an aggressive power stealing the land of a poor, Catholic people and claiming justification in Anglo-Saxon racial supremacy.

Mexico’s fate was just like Ireland’s, with the USA playing the role of the hated British Empire.

Irish soldiers quickly started to appreciate that they were on the wrong side of this Mexican tragedy.

John Riley's Mexican Solidarity 

In April 1846, one John Riley (of Cliften, Connemara), abandoned his post at Matamoros in north-east Mexico. He found his way to General Pedro de Ampudia and enlisted as a Lieutenant in the army of the Mexican Republic.

Riley was soon enough joined by over 700 other defectors – mostly Irish – who formed up as a discrete unit in the Mexican Army under his command: the St Patrick’s Battalion.

They quickly developed a reputation for courage and skill as Mexico fought battle after battle to try and hold the invaders back.

The San Patricios gave their all at the Battles of Monterey (7th July 1846), Buena Vista (23rd February 1847), Churubusco (20th August 1847), and others.

And on every battlefield, they could be picked out by their striking battle-standard, designed to evoke the Irish-Mexican solidarity against imperialism which was motivating the San Patricios.

Though the original doesn’t survive, it was vividly described by a US war correspondent:

“The banner is of green silk, and on one side is a harp, surmounted by the Mexican coat of arms, with a scroll on which is painted ‘Libertad por la Republica Mexicana’. Under the harp is the motto of ‘Erin go Bragh!’ [‘Ireland Forever’] On the other side is a painting…made to represent St Patrick, in his left hand a key and in his right a staff resting upon a serpent. Underneath is painted ‘San Patricio’.”

A memento against American Imperialism 

It’s a sad fact, but the courage of the St Patrick’s Battalion didn’t manage to drive the imperial snakes out of Mexico. The military power of the US government was just too strong.

Mexico, disarmed and with a gun to its head, was forced to cede a huge chunk of its sovereign territory – including most of modern California and Texas. (Ironically, it’s these states which Trump is now trying to cordon off from Mexico and the rest of Latin America with that absurd wall.)

Nevertheless, the Irishmen of the St Patrick’s Battalion live on as a monument to international solidarity against imperial aggression.

Amid today’s festival of all things Irish, then, spare a thought for the San Patricios – Ireland’s finest.

Erin go Bragh!