During peace time, what do people in the military do all day?

I don't understand how the military can employ so many people, in so many different jobs. Some jobs make sense: a mechanic is fixing stuff all day, boot camp instructors are training a new batch of recruits every day. And obviously there are all the jobs that have one to one civilian comparisons like a JAG Lawyer.

But how can so many people be employed full time? What are these people doing for eight hours a day? Is a sniper practicing shooting eight hours a day? Is a fighter pilot doing flight training eight hours a day, forty hours a week? Is a bomb expert fiddling with explosives for eight hours a day?

I'm not trying to knock anyone in the military, I just genuinely don't see how this system can work.