This book provides a detailed picture of foreigners who performed military service in the Principality of Transylvania over almost one and a half centuries. It explores their social and cultural background, their motivation for seeking employment in these parts of the continent and their performance within the ranks of an army fighting on the borderlands of Christian Europe. 
By focusing on the particular case of Transylvania, the author offers new insights and data on the global process of military migration and mobility in the early modern world. Readers will find a comprehensive analysis of a military system, situated at the crossroad of Western European and Oriental (Ottoman) influences. Using a wide variety of historical sources, the author reconstructs the complex process of adopting and adapting military innovations through the employment of foreign war professionals. 
This book is primarily addressed to scholars interested in migration studies, global history, social and military history. It also targets a larger audience consisting of students and passionate readers interested in the history of Transylvania and East-Central Europe in general.