“Woe to the inhabiters of the earth and of the sea! For the devil is come down unto you, having great wrath, because he knoweth that he hath but a short time” (Revelation 12:12).
The above passage from Revelation tells us Satan has declared all-out war on God's saints. It also mentions that the devil has a deadline to complete his work: “Because he knoweth that he hath but a short time.”
As followers of Jesus Christ, we are to constantly be aware that the devil is out to destroy us. Therefore, Paul says, we need to know as much as we can about the enemy’s tactics and plans: “Lest Satan should get an advantage of us: for we are not ignorant of his devices” (2 Corinthians 2:11).
Peter gives us this warning: “Be sober, be vigilant; because your adversary the devil, as a roaring lion, walketh about, seeking whom he may devour” (1 Peter 5:8). This does not mean the devil is hovering in the cosmos somewhere, giving orders to his demonic hosts. We know that Satan was cast down to earth when Christ defeated him at the cross. Thus, the devil’s kingdom is limited to the here and now (see Revelation 12:19).
Contrary to the thinking of some Christians, Satan does not possess omnipotent power. He has been defeated by Jesus and stripped of all authority. Nor is Satan omniscient, meaning that he cannot read minds. And he is not omnipresent—he cannot be everywhere at one time. He is limited to being in one place at any time.
But Satan does have principalities and powers stationed throughout the earth and his host of demons feed him intelligence at his beck and call. They hear you when you pray, and they see your obedience to God. And that is what stirs up Satan’s wrath against you!
The reference in Revelation 12:12 that says the devil knows he has only a short time is not about the time Satan has left before the return of Christ. Rather, it is about continual deadlines, a series of short times the devil has in which to accomplish his work. It is all about the brief times he has to make war against God’s saints!