This is a study of an almost inaccessible area of the intricate linguistic fabric of Afghanistan - namely, its secret codes of communication. The text draws on a profound knowledge of Afghanistan and neighbouring regions, as well as the cultural and sociolinguistic processes at work across Eurasia. The author situates these sociolinguistic matters within the appropriate diachronic and comparative background, and traces the numerous threads which connect them to areas both close to and distant from Afghanistan. The book will be of great interest to scholars from a wide range of disciplines, including, but extending beyond, the realms of linguistics, cultural history, and sociology. It will also be of practical value in many areas, notably with regards to military and political issues, as well as humanitarian aid.