He attended national school, leaving at fifteen to work in London as a postal clerk, and subsequently for the New York Guaranty Trust overseas branch. He was active in the Gaelic Athletic League and later the Irish Republican Brotherhood. His gregariousness and athletic prowess earned him the nickname "the Big Fellow."
Collins returned to Dublin in 1916 to take part in the Easter Rising. Interned at Frongoch, he was released later that year and was elected to the Sinn Fein executive in early 1917. During the next three years he became a master at eluding the British while working under their very noses. He organized rebellion activities, became President of the IRB and orchestrated a terrorist campaign against British forces in Ireland earning a price on his head of 10,000 pounds sterling. In late 1920, he masterminded the assassination of 14 top British Secret Service agents in Dublin, an event later to be known as Bloody Sunday.
When British Prime Minister David Lloyd George organized treaty talks, Collins, at President de Valera's insistence, reluctantly joined the Irish delegation. Outmaneuvered by the "Welsh Wizard," the Irish delegation signed a treaty that partitioned Ireland. A narrow vote in favor of the Treaty split the country into two factions, the Free State forces and the Irregulars. Civil war began. De Valera resigned; Arthur Griffith became President of the newly established Irish Free State with Collins Commander-in-Chief of the army. On August 12, 1922, Arthur Griffith died of a massive brain hemorrhage. Ten days later, while on a tour of his home county of Cork, Michael Collins was ambushed and shot dead at Bael na mBlath. Even today, details of the shooting remain a mystery.