This book is the second volume in a series of general histories covering the period from the 4th century to the present day. It focuses on the major political and military events of the Middle Ages, including the Crusades, the Mongol conquests, the reform of the Church, and the Investiture Controversy. It also covers social and cultural history, such as the feudal system, the emancipation of cities, industry, commerce, science, and the arts. Several sections are devoted to the history of individual European peoples, and the final chapter traces the history of the Turkic peoples.