After using the Nine Tailed Fox to attack Konoha, Obito Uchiha didn't feel like he'd quite done enough to his home village. He was planning a second attack but was talked out of it by Itachi. Believing that Obito was Madara, Itachi promised that if Obito left the rest of the village alone, Itachi would carry out the revenge on the Uchiha clan that both Madara and Obito desired. Obito agreed, and gave Itachi a role in the Akatsuki.