When Nymeria arrived on the shores of Dorne after the Rhoynar's traumatic flight from the Valyrian onslaught ; she found it a harsh desert , divided by a dozen petty king each hoping to unite it under his own banners.
These wars were fuelled by the Stormlands and the Reach who each would support a king in an attempt to gain influence . House Dayne was an exception in that it would not be supported by neither of the Kingdoms but survived mostly independently with only informal aid from northern sympathizers.
The Yornwoods, the Martells, the Daynes and the Ullers stood as the only contenders who had any hope of uniting Dorne but none could hope to triumph over the other three . This changed with the arrival of the Rhoynar near sunspear . King Mors Martell and Princess Nymeria had sealed an alliance in marriage ; in return for allowing the Rhoynar to settle in his lands, Nymeria would aid the Martells in the quest to unite the Dornish peninsula .
They were met with success at first , securing the entirety of the Greenblood river and conquering much of the Salty shore aided by the battered albeit still massive Rhoynish fleet which was uncontested in the Dornish shores (none of the Dornish kings having the capacity to build fleets of their own ).
However things became more complicated afterwards as the other Dornish kings realised the threat posed by the success of the Martells not just in military terms but in terms of the foreign culture the Rhoynar brought which threatened long standing traditions.
As is common in many conflicts, sworn enemies were united to stand against a seemingly foreign enemy (the fact that Andal and even arguably First Men traditions also counted as foreign to Westeros was conveniently forgotten ).
This alliance of Dornishmen opposed to Martell dominance was supported surprisingly by the Durrandons, Lannisters and Gardeners who for all their hatred for each other, saw the danger that a united Dorne could be . This support came mostly in the form of funds and "volunteering " knights who fought for the newly dubbed Western alliance (In reference to most of its participants' lands being West of Greenblood ).
However the support would remain mostly nominal as none wanted to commit to the conflict only to have that being taken advantage off by the other two .
Still Dorne being the least populated of all the kingdoms every soldier counts and the additional forces proved to be a boon.
The Martell's momentum suddenly ground to a halt as they started to face forces much larger and in most cases better equipped than them . Undaunted the forces of the sun banner instead avoided any decisive actions and instead resorted to skirmishes, assassinations and sabotaging supply lines among other tactics to negate the numerical advantage.
The enemy seeing through this responded in kind , poisoning Wells, sacking any settlements they found and sending saboteurs behind enemy lines. This war is unique in Westerosi history for its lack of large scale battles.
There would only be two real army clashes in the entire conflict: The sack of Starfall and the battle of Planky Town .
The first came as a result of House Dayne's shifting allegiance in the war . At first they had supported the Martells but once their fortunes changed had tried to change sides to the Western Alliance . Informed of this by their spies the Martell-Rhoynish forces launched an attack and after a bloody managed to take the castle. Though most of the family had succeeded in escaping to Andalos beforehand, King Daren Dayne and his two eldest sons remained behind .
Though the king was killed in action, his sons were not so fortunate their horrendous fate being well known throughout Westeros . House Dayne still survives to this day as a trading house in Bravos but have abandoned any hope of reclaiming their now ruined lands . Instead they are content with living comfortably and searching for the missing Dawn (the legendary sword being lost in the Sack ).
The battle of Planky town however would be the one that decided the war . The Western Alliance , in an effort to finally end the war in their favour had hired the Iron Company in an effort to match the Rhoynish fleet and to transport troops directly to the heart of Martell power .
The battle was legendary, though the Rhoynish fleet was larger than its iron counterpart, its crews were inexperienced when it came to actual naval battles which made them easy prey for their battle hardened Ironborn counterparts. To make the matters worse for the Martells many of their ships were heavily damaged and barley floating when the attack started .
This allowed troops to land and begin their attack on the trading town. Still the Martells and their Rhoynish allies did not surrender with men and women alike picking up any sharp object they can find and resisting the invaders with everything they had .
The battle was nasty, bloody and thuggish but the tide at last seemed to go in favour of the alliance but Nymeria had one last trump card to play. Boxed in and with no hope of escape Rhoynish ships began to explode in flames bringing enemy ships down with them .
The Princess had packed many of her ships with Wildfire to prevent them from being captured and with the battle going against them ordered any ship with no hope of its crew escaping to light their caches .
Though in totality less than a dozen ships actually went up in green flames, the explosions were enough to make the Iron Company captains weary of losing their ships and deciding that the pay wasn't worth losing their ships abandoned their employers who were pushed back by the defenders. To this day the inhabitants of Western Dorne still hold the Ironborn in contempt for their cravenly escape.
Nevertheless the loss of the battle resulted in the fracture of the alliance as each kingdom blamed the others for the defeat and withdrew their support. Still the Martells were too exhausted to attempt to conquer the entirety of Dorne and so signed a peace ; resigning themselves to ruling the Eastern parts of Dorne .
They would carve a prosperous kingdom out of the Harsh deserts , the surviving water wizards aiding in massive irrigation projects and trade with the summer isles making the East Dornishmen rich from the trade of exotic goods and hardwood.
Their Western counterparts also had peace amongst themselves as none dared to give their eastern rivals an opening to finish what Nymeria started .
Overtime the Eastern and Western Dorne would become radically different; one more green, heavily influenced by Esossi and summer island traditions and relying on its fleets while the other was mostly a desert, mostly Andal in its culture and mainly land based.
But if there's one thing they both share it's their mutual hatred for each other