Peter Connolly & John Gillingham 
Hutchinson Dictionary of Ancient and Medieval Warfare [PDF ebook] 

The Dictionary of Ancient and Medieval Warfare provides a comprehensive guide to the battles and wars, commanders, tactics, formations, fortifications, and weapons of war in Europe, North Africa, the Middle East, India, China, and Japan from the beginning of recorded history to the 16th century. More than 3, 000 entries, written by expert military historians, cover all aspects of warfare from the emergence of the earliest walled cities in the Ancient Near East up to and including the period of European discovery of the New World. The Dictionary is unique, the only work to cover 3, 500 years of military history. Expert authors writing in their specialty have created the most comprehensive and accessible reference work ever produced on this subject.