Part 1: Prologue
The Fourth Shinobi War - a war that was started by a mysterious man named Tobi who happened to be the leader of a certain organization called Akaktsuki (meaning Daybreak or Red Dawn). The group consisted of twelve members which usually travel in pairs. The members were the following: Black Zetsu, White Zetzu, Deidara, Hidan, Itachi Uchiha, Kakuzu, Kisame Hoshigaki, Konan, Nagato, Obito Uchiha, Orochimaru, and Sasori. These members where all from different countries (and where labeled S-rank criminals) such as: Amegakure, Sunagukure, Konohagakure, and so forth. Their main goal was to capture all the tailed beasts (known as bijuu: and their hosts (called jinchuuriki)). The purpose of this was to revive the juubi, the ten tailed, which is done by gathering all the tailed beasts together into the Gedo Statue. Once all the tailed beasts had gathered, the Gedo Statue becomes alive, and as such, it progresses to become the juubi. However, Tobi's goal is not only to revive the juubi but also to cast a genjutsu on the moon, and create "peace" throughout the world. In other words, he wants control of the world through this genjutsu which is called Tsuki No Me (Eye of the Moon Plan). This is where the war started, one man against the five Kage (leaders) and the Allied Shinobi Force.
The Shinobi Force consisted of the six major Nations: Lightning, Water, Earth, Wind and Fire, as well as the land of Iron (which is mainly made up of Samurais). The leader of the alliance is the Fourth Raikage, and his right hand man, Gaara (the Regimental Commander). The purpose of this alliance was to stand up together against the threat of Akatsuki and the tailed beasts. This was formed in the Five Kage summit, where Tobi's made a declaration of war against the six nations because of their refusal to hand over the Hachibi and the Kyuubi. Meaning, they would not hand over Naruto and Bee without a fight. At least that was the proposal, and so it was that Tobi made the declaration of war against the nations, and thus the Shinobi Alliance Force was formed. However before we jump into the war, we need to learn where chakra came from...
Chakra…what is it? Where does it come from? Well in order to know all of this, we first need to know its origins: Kaguya Otsutsuki. She was the head of the Otsutsuki clan. It is said according to the legend that she had consumed a fruit from the Shinju Tree, which bore a fruit of Chakra every thousand years was a devine tree, and thus it was forbidden to eat from it. Kaguya was longing for peace and she believed she needed a godly like power to end the human's conflict. As a result in order to end the conflict she defied the rule that she could not eat of the fruit of the Shinju tree. Therefore, she decided to ignore the forbidden rule and thus she gained that power. That ended the wars, on her own, and therefore she become the Rabbit Goddess. Sometime later, she had settle down, she eventually became pregnant, with twins. She had two sons Hagoromo and Hamura Otsutsuki. Soon after their birth she began to lose her trust in humanity as the power she had now corrupted her. However contrary to popular belief, it was her ideal way to create peace by trapping her victims in the Infinite Tsukuyomi and converting them into White Zetsus'. The public find out about his ideal and their view of her being a Goddess changed soon after this deed was found and so the public view of her being a goddess, change to that of a demon...
Hagoromo and Hamura were twins to be exact. They however had a slight differentially; they had inherited their mother's chakra and thus became the first humans who had ever inherited with chakra. It wasn't long after they were born that she decided that their chakra was hers and so it was that she fused with the Shinju tree and became the Ten-tails, which ravaged the land to attempt to recover what was his, the chakra from Hagoromo and Hamura. The three (Hagoromo, Hamura and Kaguya) had many battles but it wasn't until the final one, that both twins, had manage to defeat the beast (their mother now fused with the tree) by sealing it within Hagoromo, this resulted to him being the first jinchuuriki. This deed and among many others led him to be known as the Sage of the Six Paths. However, his death would soon come to an end (so do all, at one point). Having little time left and knowing that his death the beast would be unleashed and the beast would try and attempt to reclaim his chakra, Hagomoro decided to separate the monster's chakra from his body and use the Creations of All Things ability to create the nine tailed beasts (bijuu). He although did not have enough force and so he sealed the ten-tailed husks by using Chibaku Tensei jutsu into the moon….
Sometime later, the objective of Madara Uchiha (when he was alive and revived by the Edo Tensei) and the Renewed Akatsuki, was to revive the ten-tails and put and Infinite Tsukjyomi on the moon, and much like Kaguya, they would put everyone in an illusion and turn them into White Zetzu. However the five Kage, refused to hand over the last two jinchuuriki, Naruto (the kyuubi's jinchuuriki), and Bee (the Hachibi's Jinchuuriki). And thus their refusal to hand over those two it was why the war began. As a result, the Fourth Shinobi War had broken out.