Prince Greg is now my friend. He seemed famous enough. Unfortunately, he isn't strong enough to take me under his wing, so I can only imagine how defenseless you must have been for him to be tempted to take you.
Build your defense Force first. Build Fortifications around your border & capital & then deploy large garrisons to all fortifications & your Capital. The goal is to make it economically detrimental for anyone to attempt to take over your country without dumping trillions worth of weapons & ammo into a costly war that will leave them depleted & also open to attack by another player.
You can build a big & strong defense force without it crippling you economically, it is the Offensive Force that costs you a fortune to build & operate, but sometimes you need to build a budget for it to have active units on the ground to aid in defense.