Finally, on the eve of Saint Patrick's Day, we remember a group of Irishmen who fought in the Mexican-American War. These guys fought on the Mexican side, mind you. And their story is kept alive by a rock band from Los Angeles. That's where reporter Richard Adams picks up the story.

Cesar Chavez Avenue, in the heart of the city's Boyle Heights neighborhood, isn't where you might expect to hear Irish drinking songs like "The Boys From County Hell."

The music might seem a little out of place here, for those who don't know the story of "El Batallon de Los San Patricios." Or Saint Patrick's Battalion. Historians disagree on some of the details, but most acknowledge that about 200 mainly Irish soldiers deserted the U.S. Army in 1846 and fought for Mexican General Antionio Lopez de Santa Anna.

Vincent Valdez plays trumpet in the band Ollin.

Valdez: “To have the courage to stand up, throw down their weapons, walk over and say you are who we side with, you're doing what we believe in, not many people have the guts to do something like that, you know.”

Led by twin brothers Randy and Scott Rodarte, Ollin pays tribute to the spirit of the San Patricios, and to the often painful immigrant experience they say Mexicans and Irish share.

Rodarte: “We both have this thing where both our cultures can laugh and cry at the same time, you know, I think we really feel each other on that. We both come under hardships but we love life too much and fear it at the same time.”

In what's become a St. Patrick's Day tradition here in Los Angeles, Ollin's annual performance of well-known Irish songs draws big crowds to local rock clubs. They thrill fans of the legendary Irish band The Pogues with their dead-on cover versions.

Scott Rodarte says the shows catch some people off guard.

Rodarte: “Some people, mostly the uninformed, they think we're doing it as a joke, or doing a parody of it. They don't realize that we really mean what we're doing. Every year its just fun, going over these songs, and it takes us months to get over it.”

Ollin's own compositions combine Mexican folk styles with a punk rock energy. Adding Irish instruments like the fiddle to a traditional huapango rhythm feels like a logical next step as on the title track of their new CD "San Patricios."

Rodarte: “The chorus kind of takes you to the gallows.”

The historical "San Patricios," the band of fighters commemorated in the album, came to that unfortunate end. The San Patricios' motivation for changing sides has always been a matter of dispute. Some say the Mexicans promised them land. Others say the Irish were motivated by sympathy for Mexican Catholics. Filmmaker Mark Day researched the topic for his documentary.

Day: “John Riley, who was the head of the battalion, said a kinder and gentler people you'll not find on the face of the earth, so he couldn't understand why we had to go and invade Mexico.”

But historians agree that the Irish suffered cruel treatment from bigoted American officers. After joining the Mexican side, they are said to have marched under a green silk banner emblazoned with a shamrock and harp. And they fought bravely, many say until the end.

When the U.S. Defeated the Mexicans, most of the San Patricios were hanged as traitors. Some say it was the largest mass execution in U.S. Military history.

Mexico has added the San Patricios battalion to the names of national heroes inscribed in gold on the wall of Congress. Every year there's a commemoration ceremony on the plaza where they were executed, as recorded in Day's film.
Day: “And the names of the San Patricios are read off, and after every name is read off, they say "murio por Mexico", 'he died for Mexico'.”

With their new record, and faithful live renditions of Irish protest songs, Ollin's doing its part to keep the legacy of the San Patricios alive.

For the World, I'm Richard Adams in Los Angeles.