Eye of the Moon Plan

The is Madara Uchiha's ultimate plan to create an idealistic world, which was later adopted by Obito Uchiha. With the Allied Shinobi Forces seeing this as nothing more than robbing humanity of their free will, they intend to foil this plan. This led to the declaration of the Fourth Shinobi World War.

The Plan
Having created the plan from studying his distant ancestor, the Sage of Six Paths, Madara resolved to gather the tailed beasts with the intention of combining them and the Demonic Statue of the Outer Path back into their original form: the Ten-Tails. Then, he would become its jinchūriki and with the god-like powers to project his Mangekyō Sharingan on to the moon, the prison of the Ten-Tails' body, to cover the world in an. The end result of the plan being that he would control every living being, ending all conflict by purging free will itself.

However, due to his poor, life-support condition, Madara could no longer actively work on the plan, and passed it on to Obito Uchiha, along with his will. Obito engineered the creation of Akatsuki, most of its members not knowing the organisation's true goals. Creating the alias of Tobi and posing as his predecessor, Obito ensured that Nagato, the figurehead leader of the Akatsuki who was to serve in reviving Madara with the Outer Path: Samsara of Heavenly Life Technique when the plan comes to fruition, believed they were collecting the tailed beasts to become a dominating power in the world as a means to peace. Obito's own reasons for the Eye of the Moon Plan is to remove the agency of all living creatures and create a reality where Rin is still alive so they and Kakashi can all be together again. He had also approached Kisame Hoshigaki and requested his participation in the plan, with the offer of freeing him of the "world of lies"; Kisame, having a life full of deception and betrayal, gladly accepted for the "world of truth" he desired so much, and, along with Obito himself and Zetsu, became the only Akatsuki members to know the truth of the organisation's goal and true leader.

Progress of the Plan
Though Obito obtained seven of the nine tailed beasts, only the final two tailed beasts: the Eight and Nine-Tails, remained out of his grasp. After Nagato's death ruined any chance of Madara's resurrection, though Sasuke Uchiha's failed attempt to capture Killer B did provide him with a fragment of Gyuki's tentacle, Obito decides to take Madara's place in the Eye of the Moon Plan. Discarding all caution and revealing himself through his Tobi guise, Obito arranged to place Sasuke and his team at the Kage Summit in hopes the ninja leaders would be weakened enough to be easily taken hostage to negotiate their freedom in exchange for the last two living jinchūriki, Killer B and Naruto Uzumaki. This, however, ended in failure, due to Danzō Shimura escaping during the chaos while combined forces of the Kage, their bodyguards, and Mifune overwhelmed Sasuke. Sending Sasuke into the other dimension with Karin, Tobi introduces himself as Madara while revealing this plan to the four Kage. However, they refuse to hand over Killer B and Naruto while forming the Allied Shinobi Forces to prevent Tobi from going through with his Eye of the Moon Plan.

At the end of the first day of the Fourth Shinobi World War, Tobi took the Kohaku no Jōhei and Benihisago that each contained one of the Gold and Silver Brothers, and having already fed the Eight-Tails' tentacle to the Demonic Statue, Tobi intends to put the plan into motion by the end of the following day. Later, while fighting Naruto by the time that his true identity is eventually exposed by both Madara's return through Kabuto Yakushi's Impure World Reincarnation and his younger opponent shattering his mask, Obito fed the Kohaku no Jōhei and Benihisago to the Demonic Statue in order to revive an incomplete Ten-Tails, claiming that the monster would still have enough power to be sufficient in completing his plan. Once joined by Madara after he defeated the Kage, Obito is scolded for deviating from the original plan due to the Ten-Tails' revival being incomplete and his own revival through a different method. Regardless, entrusting Obito to make sure no one interferes as he battles Naruto and Killer B, Madara decides to capture the Eight and Nine-Tails personally to complete the plan while there is still time.

Trivia

 * Obito has blamed Naruto for the plan's slow progress, due to his constant interference causing him to deviate from the plan as Madara envisioned, despite the plan eventually involving capturing Naruto.
 * Obito noted that he would eventually synchronise Sasuke Uchiha with the statue.