In the 20th century, much of the conflict between Irish Protestants and Catholics or between English and Irish was described in political terms—Unionism vs. Nationalism. Tanner (Croatia: A Nation Forged in War) argues that the real conflicts in Ireland have always been religious, between Protestants and Catholics. In exhaustive, and exhausting, detail he traces the rise of this animosity from the 16th century to the present, arguing that the mid-16th century was crucial for Protestantism in Ireland. In 1538, the Protestant authorities attacked pilgrimages, shrines, monasteries and the cult of saints. They also demanded that churches order the new English translations of the Bible. By the 17th century, Protestant Bishop James Ussher denounced the Catholic Church in a backhanded way by arguing that the Church of Ireland was doctrinally closer to the Church of St. Patrick than to the Catholic Church. By the 20th century, Tanner concludes, the rise of a multicultural and multiracial Ireland rendered the once-certain divide between white Catholics and white Protestants superfluous. In addition, he asserts, both Catholics and Protestants are now declining so substantially in size that the battles that once raged between them no longer have tremendous significance. Tanner's thesis is rather unremarkable—a simple look at recent headlines will reveal that Ireland's struggle is religious rather than political—and his writing is plodding and dense, full of turgid prose and cluttered with detail. Readers will have to turn elsewhere for a crisper study of Ireland's religious history. (Jan.)