According to the Apostle Paul in Eph. 6:11, putting on the whole armor of God allows one to resist or stand firm against the craftiness or schemes of the devil. In other words, if one does not put on the complete armor of God, then Satan will take that person out by means of deception. One commentator describes how this craftiness can work: Mention of the schemes of the devil reminds us of the trickery…by which evil and temptation present themselves in our lives. Evil rarely looks evil until it accomplishes its goal; it gains entrance by appearing attractive, desirable, and perfectly legitimate. It is a baited and camouflaged trap. Nevertheless, we must identify his schemes if we are to fight against them.
These schemes are targeted towards our thought life initially. What are some of the general ways these schemes come to our minds? It’s anything that seeks to distract or discourage us from walking by faith in obedience to God’s will. It could be jealous thoughts, bitter thoughts, selfish thoughts, boastful/self-exalting thoughts, fearful/self-preserving thoughts, dwelling on perceived or real offences and/or blame-shifting to make excuses for sin. Of course, there are many others, but that list represents the large bulk of them.
So we must not think that Satan’s primary work is what we see in the life of Job—the physical destruction of one’s family, estate and body. Rather, Satan primarily works through enticing lies for the ultimate destruction of one’s soul. That being said, he is not an equal adversary of God; rather he is part of God’s creation and under God’s rule. Therefore, God knows his ways and knows what we need to do to resist him. And the key word in that sentence is resist. Notice the goal—not to go on the offensive against Satan, we don’t have to because he is coming against us so what we must do is stand firm against his onslaught of deceit.
 Klyne Snodgrass, The NIV Application Commentary-Ephesians, Grand Rapids: Zondervan, 1996, 339.