Before Harry ever entered Hogwarts, Professor Trelawney made a prophecy about a child who would have the power to defeat Voldemort. The child would be born as the seventh month ended, and their parents would have defied Voldemort three times. Harry Potter was born on July 31. Neville Longbottom was born on July 30. Both families had fought against Voldemort. Suddenly, there were two possible candidates. But Voldemort only knew part of the prophecy. Through Severus Snape, he learned enough to believe that the prophecy referred to Harry. And there was another detail that may have influenced his decision. Harry was a half-blood, just like Voldemort. Neville was a pure-blood. Voldemort saw Harry as the greater threat. So he went after him. And that decision changed everything. Voldemort attacked baby Harry with the Killing Curse. But instead of killing him, the curse rebounded. Harry survived, Voldemort lost his body, and the famous lightning-shaped scar was created. In trying to destroy his future enemy, Voldemort accidentally created him.