As leader of the Irish Republican Brotherhood and then the Irish Republican Army (IRA), Michael Collins developed a bold new strategy to use against the British administration of Ireland in the early twentieth century. His goal was to attack its well-established system of spies and informers, wear down British forces with a sustained guerrilla campaign, and force a political settlement that would lead to a free Irish Republic. That the Irish insurgency succeeded was not just a measure of Collins's revolutionary genius, as has often been claimed. British miscalculations, overconfidence, and a failure to mount a sustained professional intelligence effort to neutralise the IRA contributed to Britain's defeat.