In case it's slipped by you…
I've already posted a pointer to photos of Ulster Special Constabulary units here on TMP. The USC, deployed in company-sized units, was heavily involved in this action of May to June 1922.
Between the end of the IWI with the 1921 armistice in Ireland and the outbreak of the Irish Civil War in June 1922, occurred the largest battle between British and Irish forces since the Easter Rising of 1916.
This odd little 'campaign', fought on the hazy border between the new Irish Free State and the province of Ulster (counties Donegal and Fermanagh respectively), saw pro and anti-treaty Irish forces fighting alongside each other against a common foe, and was the only instance of troops of the new Irish National Army fighting British forces, which included regular infantry, armour, artillery, and aircraft (in a spotter role).
The fighting also involved amphibious operations on Lough Erne, and saw the emergence of a popular heroine in the form of the owner of the commandeered steam yacht 'Lady of the Lake' (rechristened HMS Pandora), Hazel Valerie Laverton-West, who took an active part in operations armed with a revolver she apparently knew how to use.
With overpowering numbers and vastly superior firepower ultimate British victory was inevitable, but the Republican side achieved some notable minor victories along the way.
There's a number of articles online. A very detailed, and reasonably unbiased account, can be found on the An Sionnach Fionn website.
