Why then did war happen happily in the millennia in which money supply was almost entirely limited? Governments have the ability to buy currency if they can't/don't want to mint new coin.

For example, states have been issuing various forms of bonds to raise money for war since at least the 1600s.

You haven’t offered any kind of explanation at all here.

If there is a ‘fight’ involved, how will bitcoin owners fight against the military industrial complex?

By removing their money from the existing system and moving it into Bitcoin. If the dollar is the air supply, Bitcoin is the plastic bag over their proverbial head.

It’s pretty easy to stop businesses from accepting Bitcoin if you are the military industrial complex.

Black markets are hard to eliminate altogether but no real threat.

They'd have to shut down the internet. If you can generate an address, I can send you Bitcoin (the role of the internet is limited to broadcasting the transaction to the network).

So, no. Perhaps for a certain class of user—someone who depends solely on an exchange—they can stop them but ultimately, no. They'd be limited to showing up with guns.

It's not nearly as futile as it seems unless people buy into the propaganda.

Why would they need to shut down the internet to prevent business from accepting bitcoin? That makes no sense. A simple regulation or tax would do it.