With over 60,000 combatants, the Battle of the Boyne, which took place on 1 July 1690 was the largest battle ever fought on Irish soil, and has long been regarded as the pivotal event of the Williamite War. But despite the Boyne's celebrated place in Irish protestant folklore, the critical engagement of the campaign was to take place the following year outside the village of Aughrim, in County Galway. Here the outnumbered and outgunned Jacobites, their backs to the wall, faced the Williamite army in a battle that was to decide the course of Irish, and indeed European history. In the first major history of the battle in forty years, Michael McNally brings vividly to life the personalities and events of the bloodiest day in Irish history. Placing the battle firmly in the context of the wider campaign, and of early modern European power politics, he uses evocative eyewitness testimony to reconstruct the events of that fateful encounter, and reveal just how close to defeat the Williamites came.