Ross Cowan was formerly a research student at the University of Glasgow where he was recently awarded a PhD for a thesis on the Roman army entitled 'Aspects of the Severan Field Army AD 193-238'. The major themes of the thesis are the organisation of the Praetorian Guard and Legio II Parthica, their recruitment, numbers and equipment. Ross also completed his first degree at Glasgow. In 1999 he was elected a fellow of the Society of the Antiquaries of Scotland.

Adam Hook studied graphic design, and began his work as an illustrator in 1983. He specializes in detailed historical reconstructions, and has illustrated Osprey titles on the Aztecs, the Greeks, the American Civil War and the American Revolution. His work features in exhibitions and publications throughout the world.

How, exactly, did Rome become master of the ancient world? This book examines and illustrates the tactics employed by the legions of late Republican and early Imperial Rome, from the evidence o f ancient writers. The greatest military machine in the Western world for at least four centuries, the Roman Army was the foundation of the Western military tradition, and its doctrines were central to the later revival of trained, drilled professional armies. Here the evidence is discussed in clear detail, and brought to life with battle plans and full colour interpretations of tactical scenarios.