Eye of the Moon Plan

The is Tobi's ultimate plan, which seems to involve using Sasuke Uchiha to synchronise with the Demonic Statue of the Outer Path, which currently holds seven of the nine tailed beasts gathered by the Akatsuki. Tobi notes that after Sasuke failed to capture Killer B and the Eight-Tails, he has been cautious for too long, and that it is time to emerge from the shadows and commence with this plan. During his attack on Konoha, Tobi named "starting a war to bring peace" as the reason for the attack, a poetic way to describe his ultimate plan.

After Tobi revealed this plan to four of the five Kage at the Land of Iron, they responded in refusing to hand over the last two jinchūriki, Naruto Uzumaki and Killer B, and formed the Allied Shinobi Forces to prevent the Eye of the Moon Plan from succeeding.

The Plan
Tobi's plan is to gather all the tailed beasts in order to fuse them back into their original form, the Ten-Tails. He will then become the jinchūriki to the Ten-Tails, giving him immense power and the ability to project a Mangekyō Sharingan on to the moon. He intends to use the moon, the prison of the Ten-Tails' body, to cover the world in an, thereby letting him control every living being, creating a world in which no war or crime occurred.

Part of his plan was to have Zetsu attract the attention of the five Kage at the Kage Summit and lure them to fight against Sasuke Uchiha. In doing so, Tobi hoped that the five would be weakened enough for him to take them as hostages to negotiate the capture of the Eight-Tails and Nine-Tailed Demon Fox. This, however, ended in failure, due to Sasuke exhausting himself almost to the point of death after combating the combined forces of the Fourth Raikage and his bodyguards, the Fifth Kazekage and his bodyguards, Mifune, the Fifth Mizukage and one of her bodyguards, and the Third Tsuchikage. Meanwhile, Danzō Shimura, the Candidate Sixth Hokage, escaped.

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 collected a portion of the Eight-Tails from the tentacle Sasuke captured, Tobi intends to put the plan into motion by the end of the following day.

Later, while fighting Naruto, he had the Demonic Statue of the Outer Path swallow the Kohaku no Jōhei and Benihisago to complete the Ten-Tails.

Trivia

 * Due to his constant interference, Tobi has blamed Naruto for the plan's slow progress.
 * After his resurrection, Madara Uchiha stated the world would be better off under the Infinite Tsukuyomi, implying he is more than likely involved in the the Eye of the Moon Plan as well.