Cornelius Nepos tells us that when Cato talked of wars, he did not mention the generals’ names, but stuck to events without ever glorifying the protagonists. He saw the military exploits themselves as important and not the pride they might inspire in noblemen who were often more concerned with their personal merit than the glory of the Roman people. However, he made a few exceptions to this rule, which, precisely because they were rare, made the individual selected appear more brilliant. I shall do likewise. I intend to present a survey that will give a full account of the body of knowledge that has been consolidated between the end of the war and today. I shall deliberately give more emphasis to general trends than to specific results, highlighting the overall picture rather than individuals as such. But, as I have indicated, I shall break my rule occasionally to point to the birth of a new idea or to show how cooperative work developed out of an individual's vision.