When Abraham Lincoln struggled to preserve our young union, more than 100, 000 Irish and Irish Americans joined the cause, with units like the Irish Brigade charging into battle -- green flags with gold harp waving alongside our star-spangled banner.

WHITEHOUSE: President Obama Addresses the Irish People

Celtic manager Neil Lennon has previously praised the Green Brigade for the atmosphere they create inside the stadium but also urged a minority to stop singing pro-Irish Republican songs.

BBC: Arrests made as Green Brigade protest is broken up