“Put on the whole armour of God, that ye may be able to stand against the wiles of the devil” Ephesians 6:11.
The kingdom of God is not only about peace. It is also about warfare against the powers of darkness. The devil with his armies are there trying to drag with himself as many souls as possible and we Christians have to fight him. We do need armor for that. There are spiritual battles happening across the world every single day in the same fashion as two or more opposing forces are fighting for influence somewhere in the world. We also fight for the souls of men and if we trust God we are going to win against Satan and empty hell from its captives.