I have not looked at every war in the bible, but I would add a different perspective here. First off, we do not have the original version of the OT to go from, but we do have broader research to draw from. For example, when God sent His angels to kill the firstborn of Egypt, what was He thinking of?
At the time of Moses, it was common practice in Egypt to present the young women to the temple when they reached womanhood. These young women were ceremoniously raped. It was Satan himself who possessed the priests or the pharaoh to rape these young girls. The firstborn of Egypt were literally Satan’s children. So, when God killed the firstborn of Egypt, He was killing Satan’s children, sending him the message that this behavior would not be tolerated.
To my knowledge, some of the mass killings were God’s assistance in establishing enlightened pockets of people by reducing the threats against them. This was the case in the flood, where God helped to end cannibalism and allow a farming (nurturing) culture to be established.
The other thing to consider, is that the OT is inspired work and not all of the stories are taking place on Earth. The large numbers given in the bible may not be all humans, they may include the spiritual battle going on in the background. Here is a quote from my third book:
When Troy was discovered some of Homer’s descriptions did not make physical sense, and thus tending to be treated as legend and not history. For example, in Homer’s Iliad he describes fifty thousand men and their horses on a physical piece of land that could not possibly hold them.
As when the stars shine clear, and the moon is bright-there is not a breath of air, not a peak nor a glade nor jutting headland but it stands out in the ineffable radiance that breaks from the serene of heaven; the stars can all of them be told and the heart of the shepherd is glad-even thus shone the watchfires of the Trojans before Ilium midway between the ships and the river Xanthus. A thousand campfires gleamed upon the plain, and in the glow of each there sat fifty men, while the horses, champing oats and corn beside their chariots, waited till dawn should come. (Homer, and Samuel Butler. “VIII.” Iliad. USA: Barnes & Noble, 1995. 126. Print.)
From Franchezzo’s explanations, it becomes clear that any war in the material world would be joined by the blood thirsty ethereal beings that he describes in the lower reaches of the ethereal world. They would certainly be cheering on the fighters to kill each other to satisfy their own blood lust. Whenever large numbers of people are referenced in inspired texts, we should be careful to consider in which of the two worlds they are resident.
Physically, 50,000 men could have fit on the parcel of land discovered outside of Troy, sitting around 1,000 camp fires. It was more like 1,000 men and 49,000 spirits in this battle. The spiritual battles that rage behind the scenes end up in the inspired works, because the prophets can see them, but we cannot.