Apart from the British military it seems that Irishmen have been more than well represented in armies around the World, for example the Saint Patrick's Battalion of the Mexican American War,

http://www.tsha.utexas.edu/handbook/...s/SS/qis1.html,

The famous Irish Brigade of the American Civil war led by Thomas Francis Meagher, a Waterford man like myself,

http://www.helenamontana.com/meagher/

The 2000 or so Irishmen who fought for Simon Bolivar,

http://illyria.com/irish/irishven.html

Spain, France and Austria had Irish regiments,

http://www3.sympatico.ca/dis.general/irish.htm
http://www.acsu.buffalo.edu/~dbertuca/g/valor.html