How the War Started

So what happened? Verse 6 tells us that he sinned, but not what he did. In order to see that we must look to Isaiah 14:12-15.
Isa 14:12-15 “How you have fallen from heaven, O star of the morning, son of the dawn! You have been cut down to the earth, You who have weakened the nations! (13) "But you said in your heart, 'I will ascend to heaven; I will raise my throne above the stars of God, And I will sit on the mount of assembly In the recesses of the north. (14) 'I will ascend above the heights of the clouds; I will make myself like the Most High.' (15) "Nevertheless you will be thrust down to Sheol, To the recesses of the pit.
Here we see the five I wills of Satan. Here we see Satan make statements of what he will do using the language of God when He makes an unconditional covenant. (See Genesis 12:2) Put simply this was the sin of pride; he had a desire for a place and a position that was not for him. In the Isaiah passage we get the what in order to get the why we must return to the Ezekiel passage.
In Ezekiel 28:16-18 we can get a since of why Satan sinned. "By the abundance of your trade You were internally filled with violence”, here we can infer that he lusted after wealth and power and was willing to do anything to acquire them. “Your heart was lifted up because of your beauty” We know by the description of him from earlier that Satan was a beautiful creature and from this we see that he knew it and became vain. “You corrupted your wisdom by reason of your splendor” because he was wise he substituted his wisdom for God’s wisdom.
In Romans 12:3 we read “For through the grace given to me I say to everyone among you not to think more highly of himself than he ought to think; but to think so as to have sound judgment, as God has allotted to each a measure of faith.”
The Romans passage sheds light on Satan’s problem. He became unsatisfied with his position and thought that he was something that he was not; he thought that he was God. Because of this he sought to take a place that was not his to occupy.