Alice gets a vision of the Volturi coming after them. So the Cullens try to convince them that Renesmee is not a threat. So they ask friends and family to come stand with them. But when someone who has it in for the Volturi shows up and tells them they should be ready for a fight. And they get ready. After the birth of Renesmee, the Cullens gather other vampire clans in order to protect the child from a false allegation that puts the family in front of the Volturi.