In conclusion, be strong—not in yourselves but in the Lord, in the power of his boundless strength. Put on God's complete armor so that you can successfully resist all the devil's craftiness. For our fight is not against any physical enemy: it is against organizations and powers that are spiritual. We are up against the unseen power that controls this dark world, and spiritual agents from the very headquarters of evil. Therefore you must wear the whole armor of God that you may be able to resist evil in its day of power, and that even when you have fought to a standstill you may still stand your ground. (Phillips)
It is clear that we are fighting a spiritual war against enemies who are far greater in numbers, intelligence, subtlety, and power than Israel had to wage war against in terms of the Amalekites, the Moabites, and so forth. In addition, our enemy is invisible.
Paul tells us to "stand," a military term for holding on to a position. In effect, before one can launch an attack, he must first hold the position he is in. In the Phillips translation, the word "against" is used four times, probably to stress the determined hostility that our enemy has. The Christian soldier is confronting something that, as a soldier, he could not overcome except that he himself also has invisible help to draw upon as a resource.
In military strategy, perhaps one of the most basic of all rules is never to underestimate the enemy. Our struggle is not merely against human foes, yet we find, in other places, that it is a war to the death. In fact, here in Ephesians 6, this idea is hidden in the Greek. It is a war to the death against supernatural forces. The word "powers" denotes those who aspire to world control, and ancient writers used the term to designate the savior gods of pagan religions. That is who we are fighting against—demons!
Our warfare, then, has all the trappings of a literal war, but it is something that we cannot see yet happening nonetheless. The qualities that we need to fight this war are not things we have inherently. We have to be given them by God. Our relationship with God is of supreme importance as to whether we are going to have the proper resources to fight this battle. We have to go to Him to get them, and we also need to be on good terms before He gives them to us.
One of the most valuable of all of these resources is the mindset that we are involved in a war. There are times when we, as a soldier, are going to face privation and hardship. There are going to be times of pain—both physical and mental. There are going to be times of sorrow that may lead us to depression or even bitterness. There will be occasions when we will be in fear and feel a great sense of insecurity. There are times we will win our battles, but other times we will lose and thus feel guilty and maybe depressed. There are going to be times of obedience that give a feeling of exhilaration and of being in control, as well as times of disobedience when just the opposite will be the effect.
There will also be times when we will be aware that God is disciplining us—sometimes in terms of punishment for sin and at other times in training to prepare us to master what we are doing. There will be times of sacrifice and even times of death. Nevertheless, all of these are part and parcel of a soldier's life.