The cult of the Sacred Heart had its origins in seventeenth-century France, where a nun, Marguerite-Marie Alacoque, had several visions in which Christ revealed to her his heart as proof of his love for mankind. The resulting cult was promoted by the Jesuit clergy in her native Burgundy before spreading more widely across western Europe, eventually gaining Papal recognition in 1856. Already popular within the lay population, the Jesuits promoted the cult further through the printed media in an effort to recatholicize Europe at a time when secularization presented the Church with major challenges. By the outbreak of war in 1914, the cult—Sacré Coeur/Herz Jesu—had come to dominate Catholic devotion in France and Germany, and once soldiers were killed or maimed in the thousands the need for spiritual solace suddenly became very acute indeed.

Claudia Schlager offers an exhaustive account of the role played by Sacred Heart during the war, examining its appeal and observance among the lay population and also its mobilization by the Catholic clergy. Devotion to the cult of the Sacred Heart was evidenced in a wide variety of ways, through prayer, the writing of songs and poetry, the creation of badges and medals, its use on flags, and the dedication of churches. Schlager examines each dimension in considerable detail, reproducing a rich variety of texts (prayers, songs, sermons) and illustrations from the smallest handmade artifact to opulent works of high artistry.

In Germany the war was understood as a form of atonement in which Herz Jesu played a prominent role—whether through the protection promised its adherents or through devotion to the cult guaranteeing the fallen a good death, and the prospect of a greatly reduced term in purgatory. In France, which claimed ownership of Sacré Coeur through Alacoque's nationality, the cult was widely regarded as a patriotic force. God had, its adherents claimed, chosen France, and the national tricolor was embellished with the heart of Jesus mid-flag. This tied in with the longstanding problem of the Church's relationship with the secular French Third Republic. Patriotism in wartime, so French Catholics reasoned, promised reconciliation with the republic and perhaps an enhanced role for religion in the country. While Herz Jesu did not want for patriotic loyalty, German Catholics were more concerned with their position as a minority within a predominantly Protestant country. For sure patriotic fervor promised to heal the remaining scars of the late-nineteenth-century struggle between Church and state, but German Catholics also looked across the frontier to the strength of the cult in the Austrian Tirol and, Schlager argues, to the universal values of European Catholicism. Thus the Pope's appeals for peace were transmitted to German congregations with markedly greater conviction than was the case in France.

She deals latterly and more briefly with a postwar cult, Christ the King, which was promoted by the papacy in 1925, as a response to the forces of secularization and republicanism in postwar European society. At a time when European monarchies were toppling, the Church offered its following a king omnipotent within and over a rapidly modernizing society. This new cult, Schlager concludes, adapted and complemented the Sacred Heart's message of compassion and atonement. Christ the King was an altogether more militant, masculine cult, monumentalized in a wave of church building and grandiose statuary.

Schlager's work is massively and systematically documented and referenced and not least through extensive exploitation of French and German public and ecclesiastical archives. Her painstaking primary research has lent her account originality and conviction and provided us with a valuable work of reference. Kult und Krieg began life as a dissertation presented to the University of Tübingen, and although the original underwent limited reworking and abridgement, like many German dissertations it bears the hallmark of its origins. She is anxious to place her work in a wider conceptual framework, but the early part of her book is so burdened with theoretical discussion that it threatens to overwhelm the engaging story she has to tell. Theoretical discussion apart, the book is thematically structured in such a way as to guarantee exhaustive coverage of almost every conceivable dimension of the subject, but at the price of a fair deal of repetition. The demands of the doctoral examining process invariably conflict with the needs and appetite of a wider readership, a problem addressed in the anglophone world by more extensive reworking and revision of doctoral dissertations prior to publication.

This is in no way to question that Claudia Schlager has a fascinating story to tell, providing her readers with some moving insights into the struggles of families and soldiers to make sense of the industrialized mass slaughter that had engulfed Europe virtually out of a clear blue sky. Consolation and courage, faith and atonement, served simultaneously to motivate soldiers in the field to acts of heroism or at least face death, their families to come to terms with inhuman loss, and the Church to define itself a role in a secularizing and often ungodly society. With the war over, and lost or won, Sacred Heart then played its part in shaping the individual and collective moral landscape of the postwar era. If the book's format makes demands on its readers, they will nonetheless find perseverance richly rewarding.