HISTORY OF THE ROMAN ARMY
Changes occurred in two areas, essentially, but most importantly in the purely military. Virtually every emperor did his best to follow some policy, whether offensive or defensive. Some conducted vast operations which occasionally brought them triumphal processions on the Capitol, while others had to conceal disasters. Others still had to wage inglorious wars that were more like police operations keeping law and order. Yet others reacted to the future they foresaw or the failures of the past and attempted to modify structures that they felt to be outdated. Secondly, the army interfered in politics. With the ruler as its head, it was a force that had to be reckoned with. In the context of a civil war it was even more powerful as it could join with the inhabitants of a province to make or break emperors. This was the 'secret of the Empire,2 that has been the subject of recent study.'