Puzzle of Elements
The Orieni-Centauri war started in 2001, I think.
Chapter 4: Fire – Centauri
Like Earth and Shri-shraba, Centauri Prime gave birth two to different sentient species: the Centauri and the Xon. The Xon were tall, fast and strong humanoids. The Centauri were, on their own way, powerful: they could generate and control fire.
When the two species met, a bloody war broke out. The Xon quickly overpowered the Centauri through their brute force and vast numbers. The Centauri begged for mercy but the Xon had none to give. But then the tide turned when the Centauri got a ruthless leader: Tuscano. The greatest firebender of his age. In that time, firebender drain the energy to feed their flames from the sun. But Tuscano discovered an alternate way to make fire, hotter fire and stronger fire. By draining energy from anger, hatred and thirst for power, Tuscano and his armies slaughtered the Xon until the last one.
And so the Centauri Republic was born. Sadly for many races in the future, the Centauri learnt all the wrong lessons from this. They believed that conquering was the only way to survive. Mercy was a weakness. When less than a generation later the Shoggren invaded, Tuscano used his armies of merciless firebenders, aided by three technomages, to drive off the Shoggren. With the ships the invaders left behind, the Centauri leaped ahead in technology and reached the stars.
While many centuries passed, the fire that drove the Centauri during the Xon War still burn and it had for some time consumed some of the unfortunate races the Centauri encountered. Until they found a race that was their equal and opposite: the Orieni.
Unlike all the other races they had discovered before (with the exception of the Minbari), the Orieni were benders. While the Centauri controlled fire, the Orieni produced lightning, the cold-blooded fire. When the two races met, it was hate at first sight.
At first, the Orieni were winning the war. Their ability to create, absorb and repel lightning was handy to drain the energy of Centauri warships or to make them suffer an overvoltage.
But the later, the Centauri retaliated by learning out to reach out their minds and influence the heated nuclear reactors of the Orieni and overheat them into exploding.
And so the war continued. The Centauri were winning but they soon ran out of fire. Both sides called it a draw and returned home to repair the damage.
The disaster that was the Orieni-Centauri war was the first step for the flame of the Republic to wither. The second step was the civil war that sparked two years later.
Decades went on and the borders of the Republic shrunk as its flame dimmed more and more. The Centauri had lost their will to conquer and let their fire spread. A hope for the flame to re-ignite flashed when the Narn homeworld was seized. But quickly the hope for renascence turned out to be the opening of Pandora's Box. The Centauri occupation not only didn't conceded them an opportunity to bring their old fire back, but also created their greatest enemy.
What was worse, this enemy was the earth and rock which couldn't burn no matter how intense the fire was. And now the earth that was the Narns threatened to swallow the diminished fire that was the Centauri and put it out for good.