Put on the whole armour of God, that you may be able to stand against the schemes of the devil. (Ephesians 6:11)

The ‘whole armour’ is the full set of equipment needed to wage warfare, and translates πανοπλία panoplia, whence English derives ‘panoply’.  Doubtless, he had in mind the Roman soldier fully furnished with helmet, breastplate, sandals and short sword.  To the Ephesians, Paul has already used the analogy of believers clothing themselves, ‘putting on’ (the verb ἐνδύω enduo, to be clothed or enveloped) the new self, the spiritual part downpayment of the new creation; but Paul would also have it known that this new spirit can come under attack.