One of the projects that I have on the go at the moment is a textbook/survey of Roman military history that will be arranged thematically, and run from the late republic (let's say the Gracchi) to the late empire, at least in the west (let's say Theodosius II, even though he's an eastern emperor). Today I've been working on the two main background chapters: the first is the historical overview, which will present a fleeting survey of Roman history over the course of the period in question, with an emphasis on those events that have special bearing on the subject matter (Roman military); the second surveys the sources, and the historiography and varied approaches to Roman military history. The first chapter is well under way - I have some material from past courses that I'm going to use for this, with some new material tacked on. As it happens, I have a good chunk for the late republic through the high empire, and less for late antiquity. Given that in some ways I feel far more comfortable about late antiquity, this is good news.
The second chapter is well underway too. The first half will present the myriad of sources at the disposal of students of Roman military history, and my plan in the chapter and the book is to incorporate as much of it as possible into my discussions. Thus, it won't be a history of the military based on the literary sources, or the archaeological evidence, or the papyri, or the epigraphy, but all of this and more (legal evidence, visual evidence, etc.). Sprinkled in amongst those overviews of the various sources will be some detailed discussions of select pieces of evidence that the problems they create and the questions that arise. So, for example, I'll take a brief look at Caesar's take on the rivalry between Titus and Pullo, Ammianus' description of his harrowing escape from Amida, Hadrian's speech to his troops in Africa (which survives in an inscription), our evidence for the soldier-poets from North Africa, the famous birthday party invitation from Vindolanda, and so forth. There'll be a few - and I'll likely have to cut down my working list to keep the discussion readable and workable.
The second half of the chapter provides an overview of the scholarship on the military (not in any way complete) and various approaches that have been adopted, and it will range from the impact of Keegan's "Face of Battle" to notions of western way of war, under which Rome would fall, and cultural readings of military history, those which look at the relationship between how war should be fought (in Rome's eyes) and how it actually was. In this discussion I'll raise the issue of military revolutions, and this, at long last, brings me to the subject of this little post.
Rome's military is famous, perhaps justly so. Its impact continued well after the end of Rome into the middle ages, and resurfaced again in late medieval/renaissance/early modern Europe, thanks in part to the influence of Vegetius (somewhat surprisingly) and the fall of the Byzantine Empire and the concomitant flood of things Roman, and Greek, to the west, amongst other things. What surprises me, however, is that no major revolutionary advance has been attributed to the Roman military. Indeed, most change in the Roman military was gradual, and this is true for nearly every aspect, from their equipment to their tactical preferences. In other words, ostensibly, there doesn't seem to have been any one thing that revolutionized Rome's military and which we could say led to its impressive string of successes, like the advent of iron weaponry, or the gunpowder. Rather, the Romans were good at a whole host of things, few if any of which could be attributed to them specifically.
The only possible exceptions - at least to my mind at this point in the writing process - might be the professionalization of the military under Augustus, admittedly a process that seems to have been under way for decades before that. When I say professional what I mean is: men were paid to fight on a permanent basis, the military became a career for a large number of people, and the state even regulated their supplies, housing, equipment, training, payment, and so forth. One issue is whether this really should be deemed a military revolution - or, like with so much else in the military sphere, whether it should be considered a specifically Roman development. It does seem to have been an important thing, and perhaps played no small part in Rome's longevity, but they gained their empire without such a thing. Could they have started with a professional military, and if they had, would they have been so successful in accruing an empire? But then, as I say, what really constitutes a professional army? Is it misleading in Rome's case because it seems to resemble modern militaries? What about the Macedonian army? Or the assorted Assyrian armies? Or the Egyptian ones? Because they organized, supplied, and supported their armies in slightly different ways does that make them any less professional?
Of course, even if we cannot attribute any particular military revolution to Rome, it's probably worth asking whether any state, kingdom, nation, or empire that could be associated with any such development actually enjoyed the level of success that the Romans did. In other words, does it matter? It seems to worked to their benefit to be good at a large number of things, revolutionary in none, and perhaps excellent in but a few.
Perhaps one important issue that I will have to consider in the book is why I think they were so successful in the first place. The Roman military succeeded because of X, Y, and Z. Another post, perhaps. Intriguingly, some answers might be sought in the armies and warfare that immediately followed Rome in the Byzantine east and early medieval west. To follow what I said above, it is perhaps significant that some military historians see "Roman military organization, training, strategic and tactical principles, and patterns of campaigning as pervasive throughout the early medieval world" (Morillo and Pavkovic 2013: 96-97). In other words, it's this sort of collection of things that are seen as representative of Roman military prowess, not any one thing.