The minute a person makes that definite decision to become a Christian, he or she sends a declaration of war to Satan and his lieutenants.
Whether the decision was in full glare of all or made in the privacy of your room with no physical person witnessing it, there is a loud announcement made in heaven and hell that another soldier has been enlisted in the army of the Lord.
We live in a fallen world. A world given to man by God to exercise control over but which man as result of disobedience, carelessly ceded to the devil. Since that time, the devil has been given so many titles, ‘Prince of devils (Matt 9:24), ‘Prince of this world’ (John 12:21), ‘Prince of the power of the air’ (Eph 2:2).