Imagine You're Caesar

How can you control a vast and diverse empire? Too many people just refuse to believe your god, because they already have a set of gods that makes more sense to them. What's more, all these religious differences are a real problem when it comes to stability within the empire. We could occupy every town, but that takes a lot of troops and way too much money. How can you turn this negative into a positive?

People really like their gods and they're not going to want to change, but what if they could all be brought under one umbrella? That would help tremendously. You could just co-opt their pantheons by calling them "angels" subordinate to a greater, more powerful ruling god. You could co-opt their seasonal festivals too.

What if some of them won't go along with it? Just kill them; the others will learn to keep quiet. Promise them unimaginable rewards after death if they'll just suffer quietly in life. They'll never know any better. Promise them that their enemies, clearly the servants of evil, will likewise be punished severely by the infinitely wise and just king of the gods. That will quell some of their anger.

Make sure all the clergy are on the same page; we wouldn't want them to suspect anything. If *they* don't comply, kill them too.

While you're at it, institute a flat tax of 10%, and make sure they understand that their eternal salvation is contingent upon honestly making their payments. God is always watching! He knows what you're thinking!

It's the solution to all your problems! It's so good, thousands of years from now people will *still* believe it!