The "A Collection of Unmitigated Pedantry" blog (frequently posted on HackerNews) has an interesting series on how non-state societies organize to achieve collective action, like raising an army. The series focuses on the Celtic people in contrast to the Romans.

I do find it quite interesting how this particular implementation of an agrarian non-state society has very different outcomes than typically envisioned by anarchist theorists, particularly in regards to power/wealth/influence concentration, the emergence of social hierarchy, warlords, and the poor living conditions experienced by those at the bottom.

https://acoup.blog/2024/06/07/collections-how-to-raise-a-tri...