Shamrock Guards were organized in September or early-October 1861. Its officer’s commissions were affirmed by State Authorities on 11 October 1861, with M. J. Brenan serving as Capt. In November 1861 the Shamrock Guards had 85 men and was an unattached company but subordinate to the First Division of Louisiana Volunteer Troops, suggesting it was the New Orleans area. Eventually a second compnay of Shamrock Guards (Co. B) was raised in late- 1861 and that company would later be subordinate to the Louisiana Irish Regiment. I suppose the Shamrock Guards Co. A (Brenan's) probably disbanded in December 1861 when unattached militia companies were ordered to form into battalions or regiments or be disbanded.