Yesterday's Irish Independent provides some details from the Columbia Rifles' manual. Chapter 1 is "Playing Paddy Right" dealing with what is expected of anyone who wants to join an Irish unit. A knowledge of Irish history - up to the 1860's, obviously - an Irish accent and some spoken Irish and, importantly, a good understanding of the importance of Catholicism to the Irish soldier.
The Independent failed to note the section on alcohol and fighting where the author says drunkeness is not essential. He then tries to explain the stereotype as it existed then.
... Irishmen may have a lower alcohol tolerance than other European ethnic groups. Former Irish Brigade Association president Liam Murphy who, while serving in the United States military once spent time training doctors to be army officers, stated, "There is a liver enzyme called ethyldehydrogenace [?] which metabolizes drinking alcohol. If a full-grown European can metabolize, say, one ounce of alcohol per hour, he must consume more than that for ethyl alcohol to show up in his bloodstream and, therefore, in his brain. If the standard is 1.0, then the Native American Indian runs at only 30 percent of the European norm and, according to the MDs I trained, the average Irishman metabolizes alcohol at only 70 percent of this norm."Put that in your pipe and smoke it.