The power of his might

Ephesians 6:10–13 (KJV 1900)
10 Finally, my brethren, be strong in the Lord, and in the power of his might. 11 Put on the whole armour of God, that ye may be able to stand against the wiles of the devil. 12 For we wrestle not against flesh and blood, but against principalities, against powers, against the rulers of the darkness of this world, against spiritual wickedness in high places. 13 Wherefore take unto you the whole armour of God, that ye may be able to withstand in the evil day, and having done all, to stand.