Welll. answering to the question that started this thread, I would say that:
When you create Monarchy, change your government to Monarchy. When you develop Communism, change to Communism.
Always keep your technological development levels high. So you will always have modern armies with good hi-tech weapons.
Then, you do not need to create a huge army when you go to war. Also, try to use some strategy instead of huge armed forces.
Focus on emey cities. You do not need to destroy all enemy units in a battle. It's preferable that you take one of his cities. The enemy will both be intimidated and ask for peace, and his units that were supported by the taken city will disappear.
Forget about huge low-tech armies. They just cost too much and don't win the war.
When you are in a time of peace, build some defensive units into your cities and change your government to Republic. Build temples, cathedrals and coliseums so you will appease the people and avoid rebellions. When in peace, invest even heavier resources on techonology.
If you do everything right, when a war time comes, you'll have your Dragoons facing enemy Horsemen. Or Armors facing Knights. It will be easy to win even with a small army. Use your strategy.
I never turn my government to Democracy. The risk of overthrown scares me. When you reach a respectable stand of power and peace, turn to Republic and build Women's Suffrage. You'll have your units free to fight in enemy soil.
When you reach the end of technological research chain (Future techs), change your government to Fundamentalist. Then you can build a gigantic cheap hi-tech army that will not cost you popularity. And win any war that comes.
I usually follow that system. And I rarely lose at King level.
