Eye of the Moon Plan

The is Madara Uchiha's ultimate plan that was later adopted by Obito Uchiha as well which the Allied Shinobi Forces intend to stop during the events 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 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, when he could no longer extend his life, Madara engineered the creation of the Akatsuki and placed their progress under the guidance of his apprentice and successor Obito Uchiha. Creating the alias of Tobi and posing as his predecessor, Obito ensured that Nagato, the figurehead leader of the Akastuki who was to serve in reviving Madara 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.

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's 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

 * Tobi has blamed Naruto for the plan's slow progress, due to his constant interference, despite the plan eventually involving capturing Naruto.
 * Tobi noted that he would eventually synchronise Sasuke Uchiha with the statue. However, currently whether his intent is to simply add another person to the depleted Akatsuki extraction team or something grander, is currently unknown.
 * Part of the plan was for Nagato to resurrect Madara with the Outer Path: Samsara of Heavenly Life Technique. Madara was instead brought back to life via the Summoning: Impure World Reincarnation by Kabuto Yakushi.