There has always been a tradition of armed resistance to the British military and political occupation of Ireland. The British government's denial of the legitimate demand for Irish independence, exercised the right to use armed struggle.
Armed uprisings against British rule took place in the years of 1798, 1803, 1848 and 1867. . The demand for independence for Ireland, though democratically expressed by the overwhelming majority of the people, was denied by the British government.
The birth of the Irish Republican Army happened after the Easter Rising of 1916. It was crushed after a week. Sixteen of its leaders were executed by the British government.
Following the Rising, a man named Michael Collins, as a prisoner of war, was sent to Richmond Barracks and later to Frongoch internment camp in Wales. He returned home to Ireland in December 1916. But it was at Frongoch where Michael Collins' ability as an organizer became recognized. And immediately following his release, he rebuilt the IRA.
In 1917, Michael Collins was elected to the Sinn Fein executive. During 1917 and 1918, his activities included: creating an intelligence network, organising a national loan to fund a rebellion, creating an assassination squad ("The Twelve Apostles") and an arms-smuggling operation. By 1920, Michael Collins was wanted by the British and had a price of #10,000 stg. on his head.