At some point, there were Four Air Nomad Territories which later dissipated into three, in which Air Nomads could live on the previously Northern Air Temple Territory, but it wasn't there's.
The Four Nations were a continous entity existing with the ideals of the Four Elements. In the year 1 ASC, The Fire Nation declares War on the World as marked by the genocide of all but one Airbender.
Throughout this time, they make Fire Nation Colonies in the Earth Kingdom and Air Nomad Terrritories.
Earth Kingdom DeclinesEdit
At the reach of the centennial visit of Sozin's Comet, Fire Lord Ozai causes the Earth Kingdom Genocide, killing nearly the entire Earth Kingdom, leaving only the colonies. He claims it as a new nation, The Pheonix Kingdom (unified with the Fire Nation of course), with himself as head, as the Pheonix King. The remaining Earthbenders rebel, but are turned in for slave trade.
The Principality of AzulonEdit
The Air Nomad Territories can be claimed easily now and become the Principality of Azulon, led by Lady Azula of the Fire Nation and a wave of colonists. They too became another affiliate of the Fire Nation, and the three joined as the Fire Empire.
The Water Tribe members go into hiding in ice tunnels in the Poles. They then begin to carve cities out of icebergs to hide amongst the natural surroundings. This was Avatar Aang's idea and managed to continue to this a very late point in history, in which no Water Tribe member was slave nor prisoner.
As they went into hiding, the Tribes became the Great Slave Territory, a fourth addition the Empire managed by Governor Qin. It was basically an immense slave trade post, and barrack.
The Earth Kingdom has a rebellion of benders, and takes back Ba Sing Se from the Fire Nation. This rebellion is lead by an Earthbender known as Bman (named for the Avatar, as Korra has passed). He kills millions of Fire Nation Soldiers in the process. He names the new nation: United Cities of Rebellion. He creates an army with five hundred foot soldiers, about fifty archers, three captains, two commanders, and one general. He sets up a government, where he is the supreme ruler. It fell after 305 days at Siege.
Military Domain of the Sun WarriorsEdit
A group called the Neo-Sun Warriors makes a new nation (still part of the Fire Empire) calle The Military Domain of the Sun Warriors, normally just the Sun Warriors.
Northern Temple ReclaimEdit
Due to the connection to the Air Nomads, the Azulon Principality deals with the Pheonix Kingdom for the Northern Temple Territory as they lost the Western Territory.
The Imperial State of Lava Edit
The Fusang Continent is discovered and transformed into the newest nation, the Imperial State of Lava (Lava Nation), named for its heightened volcanic activity that power firebending greatly.
The Great RebellionEdit
Slaves escape the Northern Azulon Territory and claim a large portion of the North-Eastern Earth Kingdom.
They then managed to triumph over the weak and small Northern Azulon Territory. They then helped the Northern Waterbenders strike back and claim the ruined Northern Water Tribe.
As their Empire expanded, they managed to claim the Si Wong Desert, and as Kyoshi once said "He whom holds the Desert masters the Earth Kingdom", and so it was, for after the Si Wong Desert was claimed, they controlled everything East of it and became a greater threat than the Empire acknowledged. They also assisted claiming the near entire North Pole.
They claimed the North-West and surpassed the Desert, and with this the whole of the North Pole was Water Tribe. They destroyed all previous slave-posts and fought (and won) over the remaining Fire Nation Slavers.
Soon, only the Peninsula holding Yue Bay stood, the last remainder of the Pheonix Kingdom.
The Fire Empire organized the military they once held strong and used to conquer the world. Over the years, without its nessecity, it grew weak, but was now regaining strength. They took back the penisula on which Omashu stands and large islands in the South Sea as well as using the Eastern Azulon Territory as a launchpoint for the claiming of Chameleon Bay. Meanwhile, larger pieces of the Tribes became Slave Territory.
The Yue Peninsula Colony grew strong and with the Empire's approval, became a nation to grow stronger and help prevent attack. They were the Yue Imperium of Provinces. The Northern Tribe was split into two pieces, The City-State of the Northern Water Tribe and the United Northern Tribes.
The Fire Empire then re-conquered much of the North-Western Earth Kingdom. as the Pheonix Kingdom. The Eastern Colony of Chameleon Bay also became its own nation. They became the Grand Monarchy of Chameleon Bay Territories. The Northern City State was reduced and the United Northern Tribes as well, leading to the United Boroughs of Kururk.
The North-Western Pheonix Kingdom expanded and grew nations too. They were the Northern Pheonix Kingdom (light-yellow), The Western Pheonix Kingdom (dark-yellow) and the Fenghuang Authority of City-States. The Water Tribe's suffering at the hands of the Fire Nation temporarily stopped and they tried to recuperate.
The newly-formed North-Western nations united as the Fenghuang Kingdom. The Pheonix Kingdom too expanded and the Grand Monarchy of Chameleon Bay Territories became a part of the Eastern Azulon Territory. Soon only the Northern City-State was left.
As the Pheonix Kingdom grew all the way past the Si Wong Desert, so was born the United Boroughs of Ba Sing Se. The Northern City-State soon fell with the entire Water Tribe.
The Pheonix Kingdom joined with the Fenghuang Kingdom, and they continued expansion.
A small South-Eastern piece of the Earth Kingdom remained. It was continuously reduced into nothingness.
A small Western island that the Empire didn't acknowledge still had an Earthbender Fort, but it too fell.
The Sun Warrior Nation agreed to join the Principality of Azulon due to its poor economic state.
- Fenghuangs are Chinese Pheonix's