John 18:36 (NIV)
But now my kingdom is from another place.
Christ clearly told His disciples and us that the kingdom of God is not of this world, but in us. Neither His disciples nor those who followed Him truly understood that. All the crusades in the Middle East, those by Alexander, the Romans or even Napoleon failed to understand this. Today, Christians are building massive churches hoping to immortalize the infinite God within their four falls, while even the temple in Jerusalem couldn't hold the Shekinah glory of God. God Almighty doesn't need a kingdom. He already has one, we're that.