Spirit Wars

Ephesians 6:12 KJV 1900

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.

Colossians 1:16 KJV 1900

For by him were all things created, that are in heaven, and that are in earth, visible and invisible, whether they be thrones, or dominions, or principalities, or powers: all things were created by him, and for him:

Colossians 3:10 KJV 1900

And have put on the new man, which is renewed in knowledge after the image of him that created him:

Colossians 2:15 KJV 1900

And having spoiled principalities and powers, he made a shew of them openly, triumphing over them in it.

As to the rest, my brethren, be strong in the Lord, and in the power of his might; put on the whole armour of God, for your being able to stand against the wiles of the devil, because we have not the wrestling with blood and flesh, but with the principalities, with the authorities, with the world-rulers of the darkness of this age, with the spiritual things of the evil in the heavenly places.

But against whom are we fighting and where?

First the Who we are fighting:

2888. κοσμοκράτωρ kosmokrátōr; gen . kosmokrátoros, masc. noun from kósmos (2889), world, and kratéō (2902), to hold. Lord of the world. Used in the NT of Satan as the prince of this world, i.e., of worldly men (Eph. 6:12, in the pl ., referring to Satan and his angels [cf . John 12:31; 2 Cor. 4:4]).

And against the Rulers Greek #746.

Spoken of the princes or chiefs among angels (Eph. 1:21; 3:10; Col. 2:10); among demons (1 Cor. 15:24; Eph. 6:12; Col. 2:15); the powers of the other world (Rom. 8:38; Col. 1:16 [cf . exousía {1849}, authority].

 Zodhiates, S. (2000)

Young, R. (1997) Young’s Literal Translation.

And where is this battle taking place:

In the lower heavens, the sky or air as the seat of evil spirits.

Lastly, what kind of a fight is this?

3823. πάλη pálē; gen . pálēs, fem. noun from pállō, (n.f.) to shake, vibrate. A wrestling, struggle or hand–to–hand combat. It was used of the wrestling of athletes and the of the hand–to–hand combat of soldiers both of which required deftness and speed. It denoted the struggle between individual combatants in distinction from an entire military campaign (strateía [4752]). Used figuratively in Eph. 6:12

(Eph. 6:12 Zodhiates, S. (2000) The complete word study dictionary: New Testament.