Allied Shinobi Forces

The Shinobi Alliance is a coalition between Kirigakure, Iwagakure, Sunagakure and the Land of Iron against the threat of Akatsuki and the Tailed beasts in the Fourth Great Shinobi World War.

The coalition was formed after Madara Uchiha's declaration of war after the Kages refused to hand over Killer Bee and Naruto Uzumaki, the jinchurikis of the Eight-Tailed Giant Ox and the Nine-Tailed Demon Fox. When Madara departed, the Kages and Mifune discuss their plans on dealing with Madara and the tailed beasts.

Purpose
The purpose of the coalition is primarily to defend the jinchuriki from Madara. The jinchuriki, once caught will complete Madara's Eye of the Moon Plan. Therefore, the coalition plans to first find the two jinchuriki before Akatsuki and keep them safe, away from the battlefield if nessessary. Beyond that, their duty is be put a united front against Akatsuki's seven tailed beasts.

Other Land's Involvement
Danzo, the acting sixth Hokage of Konohagakure, fled the summit as Sasuke Uchiha and Taka made their way towards the Kage. Because of this, Konoha's involvement with the coalition is in question, though the Tsuchikage Onoki suggested that Kakashi Hatake not only take the role of Hokage, but also the leader of the coalition, similar to the summit's decision of having Konoha lead the alliance against Akatsuki.

Amegakure's involvement with the coalition is also in question, being the former headquarters of Akatsuki. However, Konan vowed alligance to Naruto after the Invasion of Pain, so it is likely that whichever way Naruto chooses to fight the war, Amegakure will be behind him.