This book follows the efforts of the Transylvanian rulers to organize and to defend their new state, during its first seven decades of existence (1541-1613). The army at their disposal inherited an essentially medieval structure that reflected the social composition of the region. The bulk of the army consisted of the so called `county flags` (noble levies and conscripted peasants from their estates), the Székely levies (troops recruited in the districts of South-East Transylvania) and the troops supplied by the Saxon districts from the highly urbanized southern parts of Transylvania. In addition, the Transylvanian army also had several groups of professional soldiers that performed permanent or semi-permanent military service: the court guard (aule milites), the garrisons of the main fortifications concentrated on the western frontier of the principality and other groups that performed military service in exchange for tax exemptions like the riflemen (pixidari, pușcași, puskások) and the guardsmen (darabontok, darabanți).
The last chapter of the book is focused on the main military campaigns in which the Transylvanian army was involved (the expedition of Giovanni Battista Castaldo in Transylvania and the Banat region 1551-1553, the „Fortress War” period 1552-1571, the Long Turkish War 1591-1606, etc.), with extensive descriptions of some of the most important pitched battles and sieges.