> How would that work when the government controls the military? Would that mean that a country's military has to remain small?

I think what you need is a serious citizen militia that controls its own equipment. IIRC, that's what allowed the American Revolution to work.

If you only have a military of professional soldiers answering to the government, the government will have much less fear of its people.

But I think focusing on government power is far too narrow, because it might so weak the elites (like the wealthy) won't the government either. The government should be small enough that it fears the people, and the wealthy should be poor enough that they fear the people, too.