Fucking firsthand experience, lots of research. There's a great YouTube channel called Lindybeige; he makes fantastic video essays on some very unique, interesting topics relating to warfare. This is where I learned of this practice of Roman slave trading, from a video where he dove into why PTSD wasn't really identified in ancient times. One of my favorite videos from him: Where does a rout begin? He talks about a formation of spearmen, 500 for the sake of example, and how/where in the formation a rout may happen. Paraphrasing Lindybeige, the obvious answer is "Well the rout would start in the front, where the fighting/killing is happening. A man realizes he's in mortal danger, decides he no longer wants to fight, turns and pushes his way through the formation- this exposes the man to his left and right. The enemy may surge forward upon seeing a man run, precipitating a rout as more men in the front decide to flee." But thinking on it further, perhaps it *couldn't* happen in the front, because those men are so fucking busy trying not to get skewered or bashed over the head, that turning their backs might be *impossible.* So then he goes on to talk about other parts of the formation. Great stuff.