I Built a Fortress on Earth That Scares the Entire Universe

I just don't understand why the earth is always invaded. Can't we defeat other civilizations before they invade? Jiang Feng, who traveled through the doomsday earth, in order to prevent the earth from being invaded again, began to develop technology, cultivate talents, revive the ancient body-refining civilization, and arm the earth into the strongest fortress! What? There is technological civilization ahead, use the sun as a cannonball to flatten them! What? Ahead is a strange civilization, let me enslave them with the Cthulhu army! What? Ahead is a magical civilization, let me send Voldemort's army to defeat them! What? Ahead is the goddess civilization, and Jiang Feng personally goes out to conquer them! What? Ahead is the highest civilization in the universe, and it will be destroyed! This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.