Militant and Triumphant fills a major gap in the historical record of American Catholicism by presenting a vivid, objective portrait of Cardinal William Henry O'Connell and his significance in the church and his times. Focusing on both the triumphs and controversies of O'Connell's career, James M. O'Toole chronicles the history of the Catholic Church in Boston in the first half of the twentieth century.

The biography begins with a lively discussion of O'Connell's Irish immigrant youth and education and his early positions as rector of the American College in Rome and bishop of Portland, Maine. O'Toole convincingly demonstrates that as bishop, O'Connell actively built his own public image while ambitiously campaigning for the position of archbishop of Boston. The most enduring success, O'Toole argues, of O'Connell's 37-year tenure as archbishop of Boston--despite a sexual and financial scandal surrounding his nephew, the archdiocesan chancellor--was his elaboration of "a personal style of leadership that was different from that of earlier bishops, changing the expectations for Catholic bishops in America by thrusting on them the role of public figures they have generally south to play since."

Throughout, the book examines O'Connell's cultural and symbolic leadership of New England's Catholic population, and describes O'Connell's role in defining American Catholicism as both "militant and triumphant" asserting its cultural vision beyond narrow denominational boundaries into broad areas of public morality, and confident of its eventual triumph over secular standards.