This book provides an in-depth biography of Cardinal Désiré-Joseph Mercier, a highly influential Belgian church figure during World War I. It chronicles Cardinal Mercier's life and role, particularly his struggle as a symbol of Belgian moral resistance and nationalism against the German occupation during World War I. The author highlights Mercier's courage in speaking up for the truth and defending his people amidst German military oppression, making him a national hero. Beyond political aspects, the book also discusses Mercier's contributions to theology and philosophy, as well as his role in education in Belgium. This book is considered an important historical account for understanding the role of the church in the European political crises of the early 20th century.