Gibbons uncovers the origins of the Partition of Ireland.

The Partition of Ireland in 1921, which established Northern Ireland and saw it incorporated into the United Kingdom, sparked immediate civil war and a century of unrest. Today, the Partition remains the single most contentious issue in Irish politics, but its origins—how and why the British divided the island—remain obscured by decades of ensuing struggle.
           
Cutting through the partisan divide, Partition takes readers back to the first days of the twentieth century to uncover the concerns at the heart of the original conflict. Drawing on extensive primary research, Ivan Gibbons reveals how the idea to divide Ireland came about and gained popular support as well as why its implementation proved so controversial and left a century of troubles in its wake.
 

(From Goodreads)