I would like to express my thanks to all who have helped me in one way or another to write this book: to Maître Henri Crepin, Deputy Mayor of Coucy-le-Château and president of the Association for Restoration of the Castle of Coucy and Its Environs, for his hospitality and guidance; to my editor Robert Gottlieb for enthusiasm and belief in the book as well as judicious improvements; to my daughter Alma Tuchman for substantial research, my friend Katrina Romney for sustained interest and to both for critical reading. For first aid in medieval complexities, I am especially indebted to Professors Elizabeth A. R. Brown and John Henneman; also to Professor Howard Garey for elucidating problems of medieval French, and to Mr. Richard Famiglietti for the benefit of his familiarity with sources in the period. For various advice, guidance, translations and answers to queries, I am grateful to Professors John Benton, Giles Constable, Eugene Cox, J. N. Hillgarth, Harry A. Miskimin, Lynn White, Mrs. Phyllis W. G. Gordan, John Plummer of the Morgan Library, and, in France, Professors Robert Fossier of the Sorbonne, Raymond Cazelles of Chantilly, Philippe Wolff of Toulouse, Mme. Therese d’Alveney of the Bibliothèque Nationale, M. Yves Metman of the Archives Nationales, Bureaux des Sceaux, M. Georges Dumas of the Archives de l’Aisne, and M. Depouilly of the Museum of Soissons; also to Professor Irwin Saunders for introductions to the Institute for Balkan Studies in Sofia, and to Professors Topkova-Zaimova and Elisabeth Todorova of that Institute for assisting my visit to Nicopolis; also to Widener Library at Harvard and Sterling Library at Yale for borrowing privileges, and to the helpful and knowledgeable staff of the New York Public Library for assistance of many kinds. To unnamed others who appeared briefly to lend a hand on my journey of seven years, my gratitude is equal.