As born-again Christians we are called to warfare. Who are we fighting with? The Jews thought that the Romans were the ones that they were fighting with. But when Jesus began His earthly ministry, He made it clear that Israel was fighting the wrong foe. Israel thought Jesus would lead them against Rome and get them free once and for all. But according to Jewish history, Israel had all kinds of different enemies and they just kept coming year after year. Jesus came to defeat the one who kept sending those armies against Israel, and set His people free forever.
Hebrews 2:14 Jesus would give His life to destroy him that had the power of death, that is, the devil.
Israel knew about the devil because some of them were demon possessed, but they underestimated his influence on people and nations. Israel was in bondage to an invisible foe who hated them and their God. No matter how dedicated to the devil a man is, the devil will still hate him. Jesus defeated the devil and then He told the people what He did in order to set them free. He tried to tell them before hand but they could not hear Him because they were all spiritually dead. No man can comprehend the things of God until He is born-again. Then he is capable of receiving revelation from the Holy Ghost.
Ephesians 6:12 We do not wrestle with flesh and blood but against the rulers of darkness and spiritual wickedness in high places.
Why did the Holy Spirit give us this verse of Scripture? Because the devil engages us in warfare according to his rules, he is so cunning that he leads us to believe people are our problem. The devil crucified Jesus but he used men to undertake the role of executioner. Of course he failed and even worse than what he imaged, because Jesus forgave the men who did the devil's dirty work! If the men who tormented Jesus ended up in hell, it was not for killing Jesus, it was because they never asked Him to save them. The devil is a spirit without a body so he cannot personally operate in the world. The devil needs a body to occupy and control; he has a large variety to choose from. He uses the power of suggestive thoughts and false promises to maneuver his prey into position.
Consider the leaders of China, Russia, North Korea and Iran. Why are they so determined to take land that they have no right to? Because their supreme leader, the devil, has always wanted the kingdoms of man under his authority. The operations of the devil are very obvious to the born-again, Spirit-filled believer. His pawns have no clue nor any interest in what motivates them.
Luke 22:3 Then satan entered into Judas, being one of the twelve.
Judas was a close associate of Jesus, he was the treasurer of the Jesus Christ evangelistic association. The devil convinced Judas that he was doing the right thing in betraying his Master. Judas watched several times where the Jews tried to harm Jesus but He evaded them. Perhaps the devil convinced him that he could keep the thirty pieces of silver and Jesus would evade the mob. Judas did not know his enemy, he did not take into account that anything contrary to the Word(will) of God is of the devil.