The key turning point in modern Ireland's history, the Anglo-Irish Treaty of 1921 has shadowed Ireland's political life for decades. In this first book-length assessment of the treaty in over seventy years, Jason Knirck recounts the compelling story of the nationalist politics that produced the Irish Revolution, the tortuous treaty negotiations, and the deep divisions within Sinn FZin that led to the slow unraveling of fragile party cohesion. Knirck's incisive analysis is complemented by a comprehensive collection of annotated primary sources that give readers the drama and flavor of this contentious battle and allow them to engage directly with the positions of key historical figures.