This question gets asked here multiple times per week. You may find these older posts of interest:

https://www.reddit.com/r/AskHistorians/comments/9mdx60/monday_methods_on_why_did_ancient_warriors_get/

https://www.reddit.com/r/AskHistorians/comments/63ujea/are_there_any_examples_of_ptsd_from_early_wars_or/dfxds3i/