This scholarly work examines the use of countersigns in medieval Europe, tracing the history of these symbols and their meanings. Leyser's erudite and detailed analysis sheds light on the way in which these codes were used in political and military contexts, and provides a fascinating glimpse into the culture of the Middle Ages. Essential reading for historians and anyone interested in the art of cryptography. This work has been selected by scholars as being culturally important, and is part of the knowledge base of civilization as we know it. This work is in the "public domain in the United States of America, and possibly other nations. Within the United States, you may freely copy and distribute this work, as no entity (individual or corporate) has a copyright on the body of the work. Scholars believe, and we concur, that this work is important enough to be preserved, reproduced, and made generally available to the public. We appreciate your support of the preservation process, and thank you for being an important part of keeping this knowledge alive and relevant.