The speed of warfare then vs. now is insane to think of. Like the fact that you know your outnumbered, but you still have the actual time to wrangle up 60k people from the surrounding towns to fight for you. Getting the troops together would have taken weeks, if not months. I guess In the mean time your enemy just sacks villages one at a time, which is a somewhat show process when you have an army of 70k men
Also why the later Roman Legions were so efficient - when you have the vast majority of your troops on hand and ready to campaign at any time, you can strike with incredible suddenness.
Knowing when to split your forces to ravage the land and when to concentrate to prepare for an enemy attack is also key - Caesar runs into that problem when campaigning in Gaul in his Commentarii several times.
At West Point, a friend asked the history instructor why we only looked at European battles during the Classical and Medieval portions of our military history courses. Supposedly, the answer was because the scale of Chinese wars were also ridiculously huge, beyond what we had time to cover. Just a few tens of millions of deaths, like every other succession.
