[philipodonnell]

You're giving way too much credit to what a war looked like >5K years ago. There were no "fighting forces", there was just however many men there were, maybe 20-30 in a clan. IIRC from people studying tribes before western civilization arrived, clan warfare was pretty much about getting 2-3 neighboring clans to temporarily gang up another clan's village, kill all the males + women who resist or sell them into slavery, raze the village and then split the remaining women up amongst the victors. Rinse and repeat amongst the victors themselves and it's just not that much of a stretch to eliminate 50% of the men from an area.