"You are a heretic of the worst stripe and you dare talk down to me boy! I am a true warrior of the Seven and a favoured of the Septon itself, you and your rabble are nothing but traitors to all that is good and holy"-unidentified lord captured in the battle of the blackrain, most likely a Tarley or a griffin
"Sadly for you my lord , history will not see it that way."-Allen's now infamous retort.
It was not surprising that the forces of Allen's Star legions clashed with their northern counterparts , after all with the former's forces laing the foundations of a new state in the unclaimed lands and the latter seeking easy conquest , it was inevitable even without the benefit of hindsight.
What was surprising however was when Allen's forces proved to not only be a match for the infamous legions but displayed the ability to defeat them repeateldy and reliably on the field, very often using the very same tactics the armies of winter often employed aganist their southern rivals, the newly born blackstar legions being a prime example being trained and drilled by Northern mercenaries (who as mercenaries often are , cared little for their home kingdoms so long as they were offered a generous amount of gold, which Allen had in plenty thanks to plundering the treasures of so many houses).
These battles in of themselves were inconsequential , the Northerners and Allen eventually signing a peace treaty , with the North agreeing to let the newly minted conqueror rule everything east of the Antlers provided their merchants and ships were given easy access to Blackwater bay ports and preferential treatment in his lands.
One might wonder why didn't the North didn't just crush the upstart with vastly superior numbers and the most likely answer is that queen Alys , still consolidating her new holdings in the Riverlands did not want to risk it prematurely in a war that might provoke the other Southern kingdoms into action , instead opting to let Allen's new realm act as a buffer between her and the Durrandeons' kingdoms. It certainly helped that Allen himself was an admitted Starkophile, who in cooperated much of the North's innovations in technology and politics into his own realm (indeed he and the queen would have frequent correspondence on many matters , developing a close friendship , best displayed when the reformer made the odorous journey North to attend the queen's funeral.
But even if the North was content to simply ignore its new neighbors , the Reach and the Stormlands were not . Though they have long dismissed Allen's escapades as doomed to fail in the wrong run (and the Starry sept even provided some token support, occasionally sending a band of paticurlay troublesome faith militant troops as "reinforcements") but now the fact that Allen seemed capable of beating the feared Northern armies made him a potential threat , if not now then in the near future .
This would lead to an unlikely alliance between the Durrandons and the Greenhands who each had their own reasons for wanting to destroy Allen's realm before he had the chance to finish consolidating all his new found lands. The Former were loath to allo yet another rival kingdom to spring up to their north and the latter because Allen's religious teachings directly threatened the authority of the Starry Sept (and by extension the Greenhands' who drew part of their legitimacy from having the seat of the High septon counted among their domains). Of course the alliance was in part to ensure that both sides focused on their mutual foe rather than take advantage of their rival being distracted.
The rest of the kingdoms did not interfere : the Lannisters and the Dornish kingdoms were too far away to care , the Vale was busy dealing with its own wars with the newly arisen Moon Confederacy and the Iron Isles didn't take sides in the conflict (instead the Iron companies offered theur services to both sides of the war.)
Still the armies of the Reach and the Stormlands outnumbered Allen's own (estimates range from modest 1 : 2 ratios to the more outrageous 1:7) and were bolestered by several faith militant companies that "volunteered" to join , with the High septon giving his blessings to the forces sent off to end the "Allenian heresies" that would come to give the conflict its name.
Unfortunately for the allies armies however it would seem that whatever gods existed were on the side of the supposed heretic this time.
It began with autumn arriving earlier than the maesters' expected just as the army was making its way out of the rainwood into the southern border of Allen's domain . The rains and harsh winds were bad enough for the morale of the troops but the muddy terrain meant that the army's heavy horse were now a burden rather than an assest. This significantly slowed the march of the troops who in addition to the adverse conditions had to suffer from food shortages as caravans were raided by Allen's scouting forces, nor could they loot any of the villages they came across as the enemy forces had already forcibly evacuated and then burned down any settlements in the army's path.
As supplies ran short , so did tempers as already arguments and disagreements between the Stormlords and their Reacher counterparts began to threaten the army's cohesion and unity. The hostility had flared to the point where the two armies almost started fighting each other but luckily their respective monarchs managed to reign them in, though they both realized that they risked losing control of their forces if there wasn't any battle soon.
Fortunately (or in hindsight unfortunately ) for them , their wish would soon be granted when the scouts discovered the supposed camp of Allen's forces nearby, seemingly poorly defended and with most soldiers unprepared for a fight.
Sensing a chance , the allied armies were quickly roused into action and with surprising speed managed to form up and form up to directly assault the enemy camp and true to the scouts' reports the enemy seemed to be wholly unprepared and easily routed , with rumors that the Heretic Allen himself was killed by his own retreated followers . Victory seemingly assured the discipline of the allies broke down as after the long weeks of the march , the troops began to loot the enemy cap for riches and some despratly needed supplies . Some allied commanders advised caution and attempted to reorganize the troops but were ignored .
And that's when the seemingly retreating forces of Allen suddenly turned back with stunning discipline and coherence and reformed their racks and proceeded to charge back at the camp where the allied forces were too busy plundering to notice them until it was too late.
In a shocking role reversal it was the allied army that was being slaughtered by the Star legion troopers. With the camp began increasingly surrounded , what remaining coherent forces remained attempted to breakthrough and retreat to their own camp. They were successful but found to their horror that their own camp was taken over by a Star legion force.
The battle soon ended with a crushing Allenian victory with the leader of the Star legions capturing many noble prisoners and though the Durrandon king managed to escape , he would soon sue for peace and sign a truce with Allen. His Greenhand counterpart however wasn't as lucky and was captured and ransomed back to his family for quite a hefty sum.
With the war over, Allen was now free to complete his project of crafting the unclaimed lands of the Blackwater into a new kingdom, only now he had more money than he could ever dream of thanks to ransoming off the many lords and knights he captured . His new realm (which would be called Blakesdom in time after the blackwater bay) was very much different from the North and the Southern Kingdoms : it was undoubtedly Andal and worshiped the Seven but uniquely it was devoid of knights or lords , instead towns and castles would be administered by a new class of bureaucrats/priests who would be trained and appointed in the new capital of Starlight*. Remarkably the new kingdom was remarkably egalitarian , allowing women to rise to high positions they could only dream of in most other areas. Most exemplified when Allen stepped down and had his only child , his daughter Antania crowned as the new queen (though the succession wasn't without controversy and many would attempt to defect over it , but these events will be chronicled in a latter section).
If the war was a glorious victory for the newly christened Blaksonian forces , it was a sobering defeat for the Stormlands and the Reach , one that would have drastic consequences in the future.