What did Peter do at the Jerusalem council to defend Paul, and what would have happened if he hadn't?

Les explains that Acts 15 records the Jerusalem council, where the Judaizers had been giving Paul trials and tribulations, insisting his gospel was not sufficient unless believers also kept the law and practiced circumcision. Peter finally wakes up and comes to Paul's defense, defending the fact that Gentiles could be saved without coming under the law of Moses. Peter asks why they should tempt or test God by putting a yoke on the necks of the disciples, a yoke neither their fathers nor even Peter and the eleven had to chafe under; it was severe. Les says that had Peter not done this, Paul's gospel, Christianity as we know it, would have died right then and there. God is sovereign and could have done something else, but as the unfolding is understood, had Peter not come to his senses and defended Gentile salvation apart from the law, Christianity would never have survived.