Battle of Aihiya Swamp

The Battle of Aihiya Swamp, fought in 45 BA (45 years before Natsuki Subaru's arrival in the new world), was a major battle between the Lugnican Royal Army and the Demi-human Alliance during the Demi-Human War. The battle is known for being the largest and deadliest engagement of the war, with casualties disproportionally being of the Human side.

Initially starting as a wider counter-insurgency effort launched by the Royal Army, the campaign quickly centered in around Aihiya Swamp, where the resistance by Demi-humans was heaviest and the leaders of the rebellion were rumored to be operating from.

By subtly exploiting and encouraging the faults within the grand strategy of the Lugnican army, particularly the emphasis on countering magic circles, the factor that had lead them to a previous defeat at Castour Field, Demi-human strategist Valga Cromwell was once again able to bait the numerically superior Royal forces into another magic circle-based ambush by allowing the destroyed structures' stored (and then unknowingly released) magic to fuel an unseen giant circle spanning across the entire area, ironically leading the Humans into a situation they had hoped to avoid.

The destruction of three armies and the loss of a large fraction of the Kingdom's manpower immediately drove the Humans on the strategic defensive, enabling further rebellion across the country. The battle ended the possibility of a centralized effort crushing the rebellion. As a result, lords and sparsely deployed units across the country were left to deal with local revolts piecemeal. Not to mention, with almost every major army on the field with almost none for reserves, the capital city was left extremely vulnerable to attack.

Location
The battle took place within Aihiya Swamp, a vast swamp system covering the southern region of Lugnica along the border of the Vollachia Empire. The massing of large numbers of Royal troops did not go unnoticed by the Vollachians, leading to a minor standoff between the Lugnican 4th Army led by Razak Gildark, ordered by Lugnican high command to watch the border, and a large contingent of the Vollachian Imperial Army.

Though the true threat of conflict with Vollachia was minimal due to Lugnica's pact with the Dragon, leaving a fourth of the Royal Army isolated from the battlefield doing virtually nothing, it was possibly that very decision that saved most of the men of the 4th Army from the slaughter.

Background
Following the outbreak of tensions between humans and demi-humans in approximately 50 BA, many battles were fought, most notably the Battle of Castour Field, ending with the defeat of a sizable Human contingent at the hands of Valga Cromwell and his MGC(magic circle) tactics. With Sphinx working alongside demi-humans to reanimate corpse soldiers, every victory and defeat only served to bolster Alliance numbers.

The deaths of major names and figures such as the Sword Saint and various members of his family however, did not seem to majorly affect the morale of the Humans, who worked to adapt to Alliance tactics. Enlisting the help of court magician Roswaal J Mathers of the prominent Mathers family, the high command of the Lugnican military began an organized effort of studying the properties and effects of MGCs, and ways to counter them. The simplest solution, for the humans, was to physically destroy them - scrubbing a few lines in the dirt, as it was.

After Castour Field, the war escalated, becoming ever more deadlier. The next three years would see major fighting between the Royal Army and the Alliance insurgents, with the Royal expeditionary armies winning several tactical victories and consistently inflicting considerable numbers of casualties to the Demi-humans, though never enough to truly exhaust the Alliance. Failure to capture the leadership of the Demi-human Alliance also significantly hampered any efforts to meaningfully end the fighting. However, morale among the Humans remained high, and the Kingdom's large population and immense pool of combat-talent ensured Lugnican leadership to expand the war.

The greatest of the planned expeditions was a campaign into the Aihiya Swamp in southern Lugnica, adjacent to Shamrock Valley, the location which was rumored to be the headquarters for the Alliance's leaders. The Aihiya Swamp, being along the most unruly and unstable of the kingdom's borders had grown into a hotbed of resistance which could not be ignored, lest a Demi-humans attempt an incursion into the capital.

Lugnica (Humans)
In preparation for the southern expedition, large elements of the reorganized Royal army were gathered in the capital and sent marching south. The Human forces consisted of many of the kingdom's knights and were aided by the elite Zellgef Squadron, numbering around 80 soldiers. Overall, the true numbers of troops are entirely unmentioned - the estimates for the total amount to at least two thousand to over ten thousand men-at-arms. Being such a massive force, the army was divided into four armies, with one designated to watch the southern border.

Total command of the army was given to Leip Barielle, replacing the previous Lord Crumère, who had been wounded in battle and died of infection. Described as a capable commander, he held several victories to his name. Fiercely loyal to the Royal Army's strategy, he would work closely with Roswaal J Mathers to quickly eliminate every possible MGC, unintentionally leading to the destruction of his own army.

Alliance (Demi-humans)
As with the humans, the statistics on Demi-human Alliance forces are also unclear, though it is known that the average Demi-human was more magically adept (and many physically) than his human opposite, meaning individual Demis on the field were capable matches against an equivalent counterpart. Most of the Demi-humans present at Aihiya Field were presumably from the local area and were joined by troops drawn upon from the wider Lugnica (possibly international) region called upon by Alliance leadership.

The general Alliance "commander" Libre Fermi took direct part in battle. Valga Cromwell's situation for the entirety of the battle is unknown, though it is likely he was coordinating attacks from behind the scenes. Sphinx took no part in the actual battle, though she did end up making an appearance.

Initial actions and maneuvers
Marching directly into Alliance territory, the campaign began immediately with the three armies engaging Demi-human troops attacking groups in sporadic fashion. The small groups of resisting rebel soldiers were quickly overwhelmed.

Concurrently, specialists of the Human side were scrambled to target MGCs, as doctrine dictated. Veteran commander Leip Barielle, familiar with the order of battle, was keen to notice the apparent lack of adaptation by the Alliance against human countermeasures, despite knowing better. His general, though not quite accurate foresight even allowed him to chastise a subordinate for relegating the Demi-humans as mere "half-beasts." Though suspicious, he ultimately pressing forward with the operation.

Unfortunately, he'd never be able to fix the crucial error nor salvage it.

Zellgef Squadron
In a little over six hours since the start of the campaign, the furious hammer of the Royal vanguard had already smashed through the entire front, obliterating any and all Alliance resistance, and never allowing their opponents the chance to form proper battle lines. Leading from the front was the renowned Zellgef Squadron, its most infamous member being Wilhelm Trias, the Sword Demon. Now at age 18, he once again displayed his talent for killing Demi-humans. Supported by the rest of Zellgef Squadron and the shield bearer Grimm Fauzen, notable in his own right, Trias took at the Alliance with such a fury and tenacity that morale had been all but shattered for the rebel troops in the area.

"'Flashes of silver sent hands and feet flying, and thrusts found throat and heart; every move was ruthless, and every blow fatal. He shredded his enemies when they approached from the side; when they tried to keep their distance, he would close the space in the blink of an eye and skewer them. One demi-human after another met their end, swallowed up by the maelstrom of this swordsman’s spirit.'"

Though it seemed as if the campaign would be one of sustained one-sided slaughter for the Humans, right on cue came the personal entry of "the Viper", Alliance commander Libre Fermi. A leader foremost, his first act in battle was to reassure his wavering soldiers, and then telling them to immediately retreat. Brandishing his blade, he challenged the primary warrior in his sights, Wilhelm, to more or less a duel on the field.

Unfortunately for Trias, the snake proved to be far more experienced and combat adept than he was; the first "round" came to an abrupt end as Zellgef Squadron intervened. Just as it seemed that the elite Zellgef soldiers were to overwhelm the Demi-human fighting alone, a sudden change in the atmosphere signaled to the next stage of the battle.

Lugnica's Terrible, Horrible, No Good, Very Bad Day
All across the swamp, a very literal change in the air began to be felt by the Humans. The air becoming denser, the smell of iron from blood and the steel of weapons replaced by the moist scent of swamp water. The feeling could be described as if one were underwater (heavy limbs, lots of external pressure, etc) even though they retained the ability to breathe normally although difficulties eventually developed. The worst part - only humans were affected. Demi-humans were left free to roam and kill at ease with no signs of being affected, leaving thousands of Royal soldiers to their mercy.

The failures of the Lugnican military's strategy and the fatal oversights of their commanders were brought to light, and despite doing everything to avoid such a situation, the Humans had somehow walked into another field of magic circles, or more accurately, one giant magic circle.

The Royal Army, who'd worked so hard to destroy the many scattered MGCs had unintentionally released the magic energy built up inside them, fueling a much larger structure underneath. Of course, for the Humans, who for the most part lacked magic affinity, there was no way of knowing all of this. It is unknown whether Roswaal J Mathers knew any of the aforementioned information beforehand.

At Aihiya Swamp, the master strategist Valga Cromwell played no special tricks. No ambushes, no encirclement, no defeat-in-detail, none of that. The plan was simple - walk up to the opponent, look at his in the eyes, and kill him, like shooting fish in a barrel. In tone with his want for a messy race war, the great spell cast by the giant circle was in no way lethal, only somewhat paralyzing the enemy. In that, the only way for the Alliance to create casualties was to get their hands dirty. Even the most green of Demi-human soldiers would walk out with a kill count typical of one several times his ability.

And with that, the main campaign was all but over. Alliance soldiers descended on the Lugnicans, and slaughtered them like cattle. To the surprise of Libre Fermi, facing off with Zellgef Squadron, some soldiers still had the will to get up and fight. Sword Demon Wilhelm Trias in particular was able to swing his sword quite nimbly even while affected by the magic circle fueled entirely off of anger, but constantly at the disadvantage, he narrowly allowed Libre to get the better of him. In the final act, Libre Fermi himself would be killed, not by Wilhelm or by any human, but by his ally Sphinx, who, needing an immediate undead bodyguard and feeling no love for her fellow Demi-human, shot holes through him, took control of his body, and fled the field, leaving Wilhelm dumbfounded and seething.

Casualty Figures
The casualties for the Royal Army are estimated at 60%, with every single soldier involved suffering some kind of effect from the magic circle. Considering only around 75% of the troops actually took part in battle, as the other 25% was guarding the Southern border, figures for the three armies is around 80%. Going further, the nature of the fighting where soldiers were simply unable to escape, probably means that "casualties", which usually refers to both injured and dead, can be translated to 80% dead, 100% casualties.

In extremely general details, the Kingdom is described to have lost 40% of its manpower, and sacrificed nearly twice as many men than in the battle of Castour Field, maing it the greatest loss of life since the start of the war.

The Zellgef Squadron of formerly eighty men was now down to eleven. Bordeaux Zellgef, Grimm Fauzen, and Wilhelm Trias were among the handful of survivors; the other sixty-nine troops, including Vice-Captain Pivot Arnancy who'd been killed by Libre Fermi, were briefly turned into undead soldiers through Sphinx's magic, but were all put down by Bordeaux personally. Overall, the Squadron was absolutely decimated, with 90% of its members dead or missing (in this case, it could be said that with 10% survivors, the Squadron was reverse-decimated).

Bordeaux survived with relatively few physical injuries, but had been mental scarred by the loss of his trusted Vice-Commander. Following the battle, he would adopt a more serious demeanor, while becoming more firmly supportive of a genocide against Demi-humans. Grimm Fauzen amazingly survived getting his throat slit by Libre, though he lost his voice permanently. Wilhelm Trias? He walked away with little injuries, more pissed off and confused than before

Aside from the death of their biggest leader, whom most of the Alliance believed was killed in action, the victory was an unparalleled success for the Demi-humans. The value of Libre was not lost on Valga Cromwell, who privately feared for the future of the war as he did not consider himself someone who could lead from the front as his fallen comrade had, though in the end this only motivated him to push further for violence.

Other Consequences
Commanding General Leip Barielle was implicated for his failure, obviously. Despite not being at fault for the loss, his name would be dragged through the mud and even the little things in his past were brought up to slander him in court. His relationships with other officers was already bad, if not terrible, and those looking to dog on him found it easy to report him for his demeanor. In other words, he was cancelled, and there was nothing he could do about it. Other officers and military figures would also be used as scapegoats for the defeat. Just as after Castour Field, the military would once again go under another period of restructuring.

With most of the Kingdom's army now dead or fighting as corpses alongside Demi-humans, Lugnica could no longer afford to fight the Demi-humans as a unified force, every battle fought from then on would be one taken to them, the Lugnicans always on the defensive. In the absence of a true standing army, local commanders took it upon themselves to defend their own territories, a losing battle in the long run.

The reinvigorated Alliance, bolstered by undead numbers and the swelling of previously neutral Demi-humans now finding a cause to fight for with victory in sight, began a nationwide mass uprising, escalating a regional conflict into an all out war of annihilation, as wished by Valga Cromwell. Ready to avenge his fallen brethren, he decided that it was about time that the horrors of war strike the heart of the Kingdom of Lugnica herself - Lugnica City.

Quote Cromwell:

"“I will open the gates of the netherworld and comfort the souls of our departed comrades with the humans’ screams and death rattles. And you yourself will lead the way. All the kingdom’s warriors shall be burned to ash in the flames of my wrath!”"