Assemble! Allied Shinobi Forces!

is episode 256 of the Naruto: Shippūden anime.

Summary
Ōnoki transports the giant turtle safely back to Kumogakure, while inside Killer B starts to train Naruto how to control the power of the Nine-Tails. At the outskirts of the Akatsuki hideout, Tokuma uses his Byakugan and discovers the White Zetsu Army beneath them then relays their discovery to the five Kage. The Allied Shinobi Forces now assemble and being divided into five platoons based on their speciality. Meanwhile at the Akatsuki hideout, Kabuto now summons his undead army from the former members of Akatsuki, the former jinchūriki, the former Kage, to elders and powerful ninja. Yamato is now being secured below of the clone of Hashirama Senju's body to bolster the strength of 100,000 White Zetsu. Kabuto and Tobi now leave the hideout, signifying the start of the Fourth Shinobi World War.

Trivia

 * In his brief début, Hoheto Hyūga is depicted with black eyes. Also, Kitsuchi's hair is depicted as part of his forehead protector instead.