Most armies where farmers who did a little bit of training in their village in the off season. They would be called up for specific battles, given a couple weeks training and then off to battle, those who survived went back home.

Very few societies could afford a large standing army. There would be one or two village watchmen to keep watch over night. The king might have a dozen guards that were well trained. The bulk of the army was farmers conscripted a few weeks before at need, and sent back home when done. The economies just couldn't support more when 95% of the total human population had to be a farmer just to grow enough food.

There were exceptions. The Romans did manage to hold large standing armies, but they were exceptions.