Despite the rich sources available, Society of United Irishmen founder and leader William Drennan is long overdue a comprehensive biography. May Tyrants Tremble fills that gap with significant new research to demolish the historical consensus that, after being acquitted at his 1794 trial for sedition, Drennan withdrew from the United Irish movement. In fact, as Fergus Whelan demonstrates using new archival material, Drennan remained a leading voice of Presbyterian radicalism until his death in 1820 and his ideals, along with those of Wolfe Tone and other pivotal United Irishmen, formed the basis of Ireland's republic. From the outset, Drennan had produced United Irish literary propaganda and Whelan offers new evidence that Drennan was 'Marcus, ' author of the most seditious material published in Dublin in 1797 and 1798. The prevailing view that Ulster Presbyterian Drennan was an anti-Catholic bigot is also shown to be baseless; on the contrary, throughout his life Drennan championed Catholic Emancipation. Whelan also shines a light on one of the great mysteries of Irish history: what happened to Presbyterian republicanism after 1798? May Tyrants Tremble repositions Drennan firmly as the father of Irish democracy, whose vision for a republic has shaped the very soul of modern Ireland.