Uchiha Clan Downfall

The Uchiha Massacre is an event that took place about 4 years prior to the Naruto plot. Itachi Uchiha killed his entire clan in a single night, save Sasuke Uchiha. It is not confirmed, but some fans hypothesize that the massacre of this clan is the assignment that the Akatsuki gave Itachi in order to become a member.

At this time, the Mangekyou Sharingan is introduced to the Naruto series.