21 November 1920 was the first “Bloody Sunday” in modern Irish history. On that Sunday afternoon, fourteen people were killed or fatally wounded when police fired into the crowd at a Gaelic football match in Dublin’s Croke Park. The causes of the Croke Park massacre have been debated ever since. Some say the massacre was a reprisal for the killing and wounding of soldiers and police by Irish Republican Army assassination squads earlier that morning. The police were looking to revenge their dead and wounded comrades and opened fire on the crowd without provocation. Others disagree: the plan, they say, was merely to stop the match and search the crowd. When the security forces arrived at the park, they came under fire from insurgents in the street; the police fired back in self-defense, and innocent bystanders were killed and wounded, either in the gun battle, or the stampede that followed. More than eighty years later, new documents may finally resolve the debate over the Croke Park massacre. In the days after Bloody Sunday, two military courts of inquiry were held: their proceedings were held back by the government, but have now been released at last. When these proceedings are combined with evidence from other contemporary sources, the causes of the massacre become clear. The police did not go to Croke Park seeking revenge: they really were planning to round up the crowd, and search for weapons and wanted men. Once they came to the park, however, a few shots were firednot by rebel pickets but by the police themselves. Spectators panicked and fled. Police panicked and started shooting indiscriminately. Their officers restored order after less than two minutes but they were too late. Nine people were dead, another five were dying, and dozens more had been injured.