As I have been working on my thesis, I found a reference which I was looking for but could not find back when I was writing my Master’s thesis. It described one of Edward I’s wars in Scotland where over the course of a few months, half of his infantry threw down their issued crossbows and headed home. The story comes from Michael Prestwitch, “Edward I’s armies,” Journal of Medieval History 37 (2011) pp. 233-244:
The logic of the way the infantry were organised, and the quality of the officers, was not, however, sufficient. Desertion was a major problem, and it did not prove possible for Edward I to keep large numbers of men in the field for any considerable length of time. For example, there were almost 3,500 Yorkshire infantry in the army when it mustered at the end of June 1300. A month later the number was down to 1,483. Edward was understandably furious, and wrote to the keeper of the wardrobe. ‘We are sending you under our seal the names of the footmen from the county of York who have left our service and our host without our leave. These people have maliciously deceived us and have traitorously failed us in our business.’ In 1301 he complained to the officials of the exchequer that as he had no money, he could not prevent his troops from leaving.
Now, a medievalist like Prestwitch can explain the customs of warfare around the year 1300 which made invading a distant country unbearably expensive better than I can (There is a handy article on the situation in Geoff Mortimer ed., Early Modern Military History, 1450-1815 (Palgrave Macmillan, 2004)). But this is relevant to a point which I make in the Doktorarbeit.
People often describe Achaemenid infantry as “reluctant levies” and explain that the kings did not trust their subjects in the provinces and preferred to rely on Persian cavalry and foreign mercenaries rather than train and equip the peasants. Eduard Meyer was trying to decide what he thought of this idea a hundred years ago (Geschiche des Altertums, Band 4, S. 63 if you read German). But in every single society with conscription which I have looked at, I find that there was a great deal of reluctance amongst the future draftees to spend years in a distant land. Kings and republics were often much more eager to recruit soldiers than to feed and pay them, provide medical care when they were wounded, and support their children if they were killed. So in every society which I have looked at, conscription for a distant war at least provokes grumbling, and usually efforts to avoid going, whether those involve legal loopholes and convenient ailments, hiding from the census-taker, or getting together to murder the conscription officer on some lonely road and hide his body. The more ambitious the rulers, the more intense the resistance. Nathan Rosenstein noticed that after Gaius Gracchus offered free land to citizens, the next census registered 25% more cives, which suggests that at least a quarter of the eligible population had avoided being registered on the list which was used to recruit soldiers. Some armies turn reluctant draftees into an effective fighting force, and others do not. So whether or not Babylonian levies were “reluctant” is about as relevant to the question of their effectiveness as the shape of their skull.