The early 3rd century AD saw the Roman Empire confronted with an increasing number of problems: the northern frontiers shattered under the impact of attacks at the hands of Germanic and Sarmatian tribes, while the Persians ravaged the Eastern provinces almost with impunity. Economic crisis, the effects of the Antonine Plague, endless usurpations and climate change brought the Roman Empire to the verge of collapse. In the year 238 AD, the Emperor Alexander Severus was murdered at Mainz by his own troops. The accession of his successor Gaius Iulius Verus Maximinus ushered in five decades of inner unrest and enemy incursions, in which emperors in quick succession constantly fought among themselves while desperately trying to stabilize the tottering Empire. The fateful era of the Soldier Emperors had begun. This book seeks to provide a concise overview over organisation, tactics, and equipment of the Roman army at the beginning of this era, and also sheds light on Maximinus' German campaign, in which Rome's army once more ventured deep into unconquered German territory. The discovery of the Harzhorn battlefield has enabled archaeologists and historians to reconstruct a dramatic episode from this dramatic time.