The writer of Ephesians does not mean, of course, to speak literally. He does not mean to encourage Christians to take up arms, literally, in the name of Christ, although - tragically - there can be no doubt that a literal interpretation of these phrases must have been acted upon countless times, by countless fervent crusaders of the cross.
On the contrary, the writer of Ephesians writes metaphorically, symbolically. S/he means that we should put truth, righteousness, peace, faith, salvation, the Spirit, the word of God in place of weapons. That instead of actual military armour we should use this ‘armour of God’ to live in such a way with each other that the other kind of armour becomes completely unnecessary and is abandoned.