This book deals with the settlement of te Companions outside Medina, and their involvement in the battle of siffīn, the battle that tore the early Muslim community apart. Based on five major biographical dictionaries written by the traditionists (ahl al-ḥadīth) of the 9th - 12th centuries, two lists are made: that of the Companions who settled in Iraq, Syria and Egypt, and that of those who were involved in the battle. Comparing the background of these two groups of Companions, the volume analyzes dividing line between the two camps. The use of a quantitative approach, and the use of the traditionists' works as the main source in the historical study of classical Islam is an important contribution to the book.