United Water Tribes

The United Water Tribes, often dubbed the Confederacy of North and South Water Tribes, is the name of the unified government of the Northern and Southern Water Tribes of Xuiz Earth being primarily located in and around the Northern and Southernmost regions of the planet near its' poles, though the term itself is actually used to refer to groups of similar cultural and ethnic backgrounds that inhabit various parts of the planet, like the Foggy Swamp in the Earth Kingdom, though that particular Tribe wasn't known until much later on when they were stumbled upon by Avatar Aang and the Southern Chief's children, Katara and Sokka.

While generally peaceful as a people, who often tried to live in harmony with nature, it does not mean that they weren't capable of fighting, far from it, they are very capable of fighting if it means defending itself from aggression, which is exactly what happened during much of the Hundred Year War and the Campaign on Xuiz. 

When the Axis discovered the planet in 1514 and made the Fire Nation a member, the Alliance caught wind of this and invited both the Water Tribes and the Earth Kingdom to join its' ranks, in essence, dragging the planet into a much larger and destructive war in the process. After they officially joined, the Old Galactic Republic, the United States of America and the Human-Vortigaunt Federation in their efforts at defeating the Fire Nation and their allies, the Empire of the Combine Race and the German Reich. 

Over the years after its' membership into the Alliance, the two tribes were becoming more and more unified, in terms of government at the very least. With some research into various allied governments, the two once largely separate Water Tribes unified under a dualistic constitutional chiefdom, with a Northern Chief and a Southern Chief have equal power over the other, but in time, both chiefs lost much of their power and were regulated to a head of state position similar to the King of the United Kingdom, a person with limited powers overall, while an elected official is the true head of government and control most of the power. From there on, the Grand Elder, the name of the United Water Tribes' head of government, is the one to actually lead the nation through much of the war. That's not to say that neither chiefs didn't have some manner of power over their tribes, they still serve as the head of their respective militaries and can lead them into battle whenever they chose, something to which the Southern Chief, Haokoda, was well known for.