This is for the naruto fans who do not know the dark history of uchiha clan.
Once upon a time there lived in the village konohagakure a girl from Hyuuga descent. He falls in love with a man named Sojobo, but he was not a member of the Hyuuga. So that their relationship is forbidden in order to maintain the sanctity of the technique doujutsu Hyuuga, namely byakkugan. But because she loved him, so they got married.
Apparently Sojobo not human. He is the devil or some kind of Tengu
of the type of Konoha tengu. Then the girl had given birth to a son, named Uchiha Madara. Uchiha name taken from a typical weapon of Konoha Tengu Fan (Uchiwa). Uchiha Madara grew into a powerful ninja and even Byakkugan has evolved into the Sharingan. Uchiha Madara friends with the first Hokage. Closeness of their friendship relations as well as Naruto and Sasuke friendship.
After Madara adults, Sojobo began to show his evil intentions. Sojobo not marry her for love, but because he wanted to get a new body. Madara knows became angry. Because he felt that he could not kill his father, he asked for help at the Kyuubi the fire god. Kyuubi that Madara was impressed with the intention to kill his father who was finally lend its strength to Madara. So that Madara could use Amaterasu stance, the fire that burned up to seven days and seven nights. However, Madara still could not kill him. Madara finally sealed with the seal Sojobo. The first Hokage at that time was leading the Konoha village, angry at Madara because he had borrowed strength and is considered dangerous Kyuubi Konoha village. The first Hokage finally feel responsible in any village of Madara, and ultimately aimed at ending their battle in the Valley of the End (where the battle between Naruto and Sasuke) by killing Madara.
The story was submitted to Uchiha Itachi. Itachi is angry because knows he is a descendant of power after the end tengu tengu. Requirements to unseal Sojobo are three users Mangekyou Sharingan and Kyuubi power. Because he has mastered the Mangekyou Sharingan, he intends to make his brother, Sasuke the Mangekyou Sharingan user second. That's why he killed all the Uchiha clan members, to make Sasuke stronger. And that's why Itachi was after Naruto.