Why did the Battle Start?

In traditional Christian theology, Lucifer was once second in command to God . However, he lusted after God's position and wished to be first. He led a revolt against God and led as many as "one third" of the other angels . He lost and was banished to the Earth to roam until Judgment Day . His followers were the fallen angels and became demons and evil spirits . The Book of Revelation states that Lucifer and his followers will be banished to Hell forever.

The Battle Continues...

Billy Graham wrote the following about spiritual warfare in his book Angels :

We live in a perpetual battlefield ...The wars among the nations on earth are mere popgun affairs compared to the fierceness of battle in the spiritual unseen world. This invisible spiritual conflict is waged around us incessantly and unremittingly. Where the Lord works, Satan's forces hinder; where angel beings carry out divine directives, the devils rage. All this comes about because the powers of darkness press their counterattack to recapture the ground held for the glory of God...

Since the fall of Lucifer, that angel of light and son of the morning, there has been no respite in the bitter Battle of the Ages. Night and day Lucifer, the master craftsman of the devices of darkness, labors to thwart God's plan of the ages. We can find inscribed on every page of human history the consequences of the evil brought to fruition by the powers of darkness with the devil in charge. Satan never yields an inch, nor does he ever pause in his opposition to the plan of God to redeem the "cosmos" from his control.