Following up on their Fenian Raids of June 1866 and readying for another Canadian invasion into British territory, the Robert’s wing of the Fenian Brotherhood met in Troy, NY for the Fenian Congress of their members throughout the country.
They reorganized their Irish Republican Army standardizing a formal military organization outlining several military orders in a Circular of September 18th 1866. This Circular was not only sent out to their Fenian Circles throughout the county but also to the national press, to show the world the Fenian Brotherhood were prepared and meant business.
The Circular included regulations for their uniforms, of course all being sold through Fenian Headquarters, the costs, regimental make up, designations as well as rank. Later, the Fenians redesignated the green jackets for the cavalry and same pattern except for blue for infantry.
Here is the official Fenian circular which was published in newspapers throughout the country around the middle of November 1866.
Source: New York World, Nov 13, 1866