Its also good too to see the way they dealt with WW2 looming. My granda joined up for the emergency and he was anti treaty. I often wonder how it had been pitched to the old IRA anti treaty side.
My grandfather, a Dubliner, was also anti-Treaty, interned in 1922-3 in the Curragh Camp and was hunger strike for a while, as hundreds were at that time. He, too, joined the 26th Battalion at the outbreak of the Second World War (Emergency). Like the majority of the anti-Treatyites, and also the even bigger majority of its voters, he had supported de Valera political line after the Civil War. So with Dev in power for years, and with a new constitution, etc. I don't think it was a problem for guys to join the Irish army at that point. Even Tom Barry, who was very militant, resigned from the IRA and joined the army at that time. The rump that was stilling calling itself the IRA shamefully collaborated with the Nazis. My grandfather, in fact, later joined a branch of the British armed services. I'm pretty sure many other members of the 26th Battalion did likewise -- both to fight Hitler and to feed their families.