Occupying a country is easy, defeating one is harder
You should try The Sling and the Stone: On War in the 21st Century. It tells how to defeat an enemy once their army is defeated. If you need to figure out how to defeat the army, read books by Douglas MacGregor. He also has ideas on how to defeat the post-conflict insurgency.
"If ye love wealth better than liberty, the tranquility of servitude than the animated contest of freedom, go from us in peace. We ask not your counsels or arms. Crouch down and lick the hands which feed you. May your chains sit lightly upon you, and may posterity forget that you were our countrymen!” - Samuel Adams