War of the Hundred Years
(Unless stated otherwise, all information herein is taken from The World of Robert Jordan's "The Wheel of Time", Chapter 4.
The War of the Hundred Years was a series of wars and battles between shifting alliances following Artur Hawkwing's death in FY 994. It lasted over a century, leading to the collapse of Hawkwing's empire and the creation of the nations of the New Era. During this time, many nations were set up and broke apart, until stability returned around FY 1117. During the early years, several people, Marithelle Camaelaine, Norodim Nosokawa and Elfraed Guitama came close to seizing the entire empire, but none were able to manage it. The destruction during this time was so great that the true year of the end of the struggles was not certain, and a new calendar, the Farede Calendar, was devised.
Formation of the Nations of the New Era
Little is revealed about the formation of the current nations, though information of questionable veracity can be found in the Role Playing Game Guide
The first countries to form were the five Borderland nations, which declared independence almost immediately after Hawkwing's death, and with the Blight as their prime concern, they avoided much of the strife of the other nations. Andor, also formed very early on when Ishara and Souran Maravaile joined to form a nation centered on Caemlyn that slowly expanded and Tear had a similar history, declaring independance on hearing of Artur Hawkwing's death, but only slowly growing in size. Of the other countries, Tarabon and Cairhien are known to have formed early in the war, and Illian towards the end (The Wheel of Time Roleplaying Game)
At the end of the war, twenty four nations remained, Almoth, Altara, Amadicia, Andor, Arad Doman, Arafel, Cairhien, Caralain, Ghealdan, Goaban, Hardan, Illian, Irenvelle, Kandor, Kintara, Mar Haddon, Maredo, Malkier, Mosara, Murandy, Saldaea, Shienar, Tear and Tarabon. Some of these, such as Andor, were largely based on provinces under Artur Hawkwing. Others, such as Ghealdan, had almost exactly the same borders as the land that occupied the area before Artur Hawkwing (in this case Dhowlan).
"There were those who would have erased even the memory of him, if they could. Books were burned just because they mentioned his name. In the end there was nothing left of him but the stories, and most of them wrong. That's what his glory came to.
The fighting didn't stop, of course, just because the Hawkwing and his kin were dead. There was still a throne to be won, and every lord and lady who could muster fighting men wanted it. It was the beginning of the War of the Hundred Years. Lasted a hundred and twenty-three, really, and most of the history of that time is lost in the smoke of burning towns. Many got a part of the land, but none got the whole, and sometime during those years the statue was pulled down. Maybe they couldn't stand measuring themselves against it any longer" (Elyas to Egwene and Perrin, The Eye of the World, Chapter 29