What happened With Nagato Uzumaki
So as we all now know, Nagato was an Uzumaki and Madara 'gave him the Rinnegan'. This is what I think happened...
-Nagato Uzumaki was born into the poor country called the Whirpool Country during the time of war
-When Nagato was born, Madara seized the opportunity to find himself a new and manipulatable vessel for the Rinnegan
-Madara transplanted an unawakened Rinnegan from the SO6P's dead body
-Madara knew that everyone in the Whirpool would be destroyed, so he waited until this took place. After it did, he allowed Nagato to do whatever he wanted, knowing it wouldn't matter in the long run
-After Jiraiya left them and Akatsuki was formed, Madara gave away intel to both sides of the war that they were dangerous, asking them to attack the group
-Nagato awakened his Rinnegan according to Madara's plans, Yahiko was killed, and Madara came out of hiding
-He told Nagato that 'peace' could only be achieved through his moon's eye plan and Nagato's pain
-Madara asked Zetsu to reincarnate the dead bodies he selected to become the 6 paths of pain
So that is what I think happened! Please Comment!