The Irish Civil War in 1922 came about as a direct result of the Anglo-Irish Treaty which was signed the previous year. The Treaty was the result of long-term battling for an Irish Republic, and was a compromise between British and Irish claims. Some felt the Treaty gave Ireland enough home rule to be acceptable, especially considering a possible alternative of war with Britain, while many others believed that nothing short of becoming a full Republic was good enough for Ireland.
After so many years struggling for independence many Irish nationalists saw the Treaty as a step back, and refused to accept it. The Irish Republican Army split over it and became the anti-Treaty IRA and the pro-Treaty National Army.
The War itself began after a British General was shot by IRA soldiers in London. His death caused Britain to threaten a retaliation with their own troops, and to prevent British interference the Provisional Government which had been created to oversee the transfer of rule from British to Irish hands was forced to take action.
The British had blamed the Four Courts garrison of the IRA, who resided in Dublin, so they were the ones first fired upon by the National Army on June 28th of 1922. This action caused IRA sects around the country to take sides, and most joined the anti-Treaty faction. Though the anti-Treaty side had numbers, the pro-Treaty side had the assistance of the British government and all its accompanying firepower.
By August pro-Treaty forces had retaken all territory that had been previously captured by the anti-Treaty IRA. The war seemed practically won, the anti-Treaty IRA was no match for the National Army. However, the anti-Treaty faction refused to give in. After the traditional war was over, they began to attack the pro-Treaty forces using guerrilla warfare. In that same month they claimed the life of Michael Collins, head of the Provisional Government.
The anti-Treaty army did whatever it could to undermine and attack the new government, and in retaliation the government took on a policy of executing any guerrilla fighters they caught. The two sides continued for some time going back and forth murdering each other’s members in a constant state of revenge against the other side. But by May of 1923 the losses had become too great and a ceasefire was called by the anti-Treaty IRA’s leader. The war was effectively ended in favor of the pro-Treaty faction, though no official surrender or negotiation ever took place.
Though the war had ended, the pro and anti-Treaty factions remained, both harboring deeply bitter feelings against the other. Extensive legislation reform over decades was able to somewhat reconcile the sides, but the topic of the Civil War remains a delicate subject to this day.