I will put enmity between you and the woman,
and between your offspring and her offspring;
he shall bruise your head,
and you shall bruise his heel.

Genesis 3:15

Genesis 3:15 is so important because this is the first direct reference in the Bible to the coming Messiah, Jesus.

In the aftermath of sin, God pronounces judgment on Satan, the power behind the serpent. The judgment is the enmity, the hostility, between Eve’s offspring and Satan’s offspring. The woman’s offspring refers to all people, including Jesus Christ. Satan’s offspring includes people who reject God, and demonic beings.
God also announces the outcome of this enmity. Satan will deliver a glancing blow against Jesus, a blow to the heel, a reference to the cross. But Jesus, by that very death on the cross, will deliver a fatal blow, a blow to the head, against the devil.

The outcome of the battle was never in doubt.

Be ever mindful: The battle is real. We ignore the battle and the enemy at our peril.

Dr. Haddon Robinson describes the attack:

When Satan comes to you, he does not come in the form of a coiled snake. He does not approach with the roar of a lion. He does not come with the wail of a siren. He does not come waving a red flag. Satan simply slides into your life. When he appears, he seems almost like a comfortable companion. There’s nothing about him that you would dread. The New Testament warns that he dresses as an angel of light … One point seems quite clear: when the enemy attacks you, he wears a disguise. As Mephistopheles says in Faust, “The people do not know the devil is there even when he has them by the throat.” … He does not whisper to Eve, “I am here to tempt you.” … He doesn’t come and knock on the door of your soul and say, “Pardon me, buddy, allow me a half hour of your life. I’d like to damn and destroy you.”

Satan slides in. He slithers. He comes to deceive, accuse, tempt, condemn.

Don’t listen! Recognize his schemes. Resist his attack. Fight the battle in Christ’s strength.