Since the Christian nations declared war on the Ottoman Sultanate one after another in April of this year, the powerful Sultanate nearly fell into a quagmire of two-front warfare.
However, after Murad II made the correct decision to first concentrate his efforts on kicking Karaman out of the war, the European part of the Ottoman Sultanate, Rumelia, bore immense pressure from the Crusaders.
Even with the diplomatic efforts of Kandar Halil Pasha and the cooperation of various generals, the Sultanate initially gained an advantage in Serbia, but this turned into a disadvantage due to the timely arrival of the Magyars and the participation of the two Wallachia principalities on the Danube.
It was under these circumstances that the Ottoman Rumelia Legion began a steady retreat within Serbia, falling back to Nis.
Nis, anciently known as Naissus, was once an important town of the Roman Empire, and the birthplace of Constantine the Great, the founder of Constantinople and Roman Emperor; it was also the birthplace of Constantine III and Justin I.
Furthermore, Serbia's oldest orthodox church was also located in the city.
And now, this was the most important military town in South Serbia; once it was controlled, the remaining South Serbia region could be said to have its gates wide open, allowing the Crusaders to advance south more smoothly.
If it hadn't been for the Ottoman Sultanate inciting pro-Ottoman Serbian nobles to betray the Autocratic State and trick open the city gates in May, George Branković would not have abandoned his capital so quickly to seek aid.
Fortunately, under the Crusaders' counterattack over several months, several lost territories of Serbia were finally recaptured.
By mid-autumn, the liberation of Serbia had reached its most crucial step: the recapture of Nis.
Facing such a situation, the Ottoman finally could not hold back and began to mobilize troops on a large scale, vowing to stop the Christian there.
Therefore, from September to the end of October, four small-scale battles successively broke out between the two sides:
The first engagement occurred in the village of Gornja Toponica north of Nis, where Transylvania Wallachia troops under Hunyadi János spearheaded the attack, destroying the Ottoman stronghold there.
The Crusaders captured hundreds of enemy soldiers and plundered the town.
Subsequently, to thwart the Christian offensive, Kasim Pasha, disregarding his colleagues' objections, ordered three Ottoman armies of different sizes but each numbering seven to eight hundred men to launch successive surprise counterattacks against the Crusaders, engaging in three battles.
As a result, under Hunyadi's command and with the cooperation of local Serbian nobles loyal to George Branković, these three forces were utterly annihilated by the Crusaders, causing the high-ranking Rumelia Governor to receive a warning from Edirne and be temporarily relieved of his supreme command in the Rumelia Legion by the Grand Vizier acting on the Sultan's behalf.
Seizing this opportunity, the militarily astute Hunyadi persuaded the young King Władysław III at the end of the month, hoping he would approve his leading a large army to retake South Serbia.
The king, eager for victory, naturally did not object; instead, he temporarily assigned his Polish cavalry to him, demanding that Hunyadi achieve a complete victory.
Although both Kasim Pasha and Turahan Bey had anticipated the major battle at Nis, they completely underestimated how swift the Crusaders' pursuit would be.
In haste, Kasim Pasha had no choice but to order Ishak Bey Hranic, the local governor of Üsküp, to lead his four thousand Serbian auxiliary heavy cavalry to provide support, while Grand Vizier Halil Pasha quickly ordered Arnavutlu Iskender Pasha to bring all five thousand of his cavalry north to assist Kasim Pasha and Turahan Bey, who could now at most deploy three thousand cavalry and ten thousand conscripted militia.
Thus, on November 3, 1443, the largest battle between the Ottoman and the Crusaders since the war began finally erupted on the plain between Nis, a major town in the southern Serbian Despotate, and the nearby Bovan Fortress.
To achieve a morale-boosting victory, the Crusaders made extremely thorough preparations: to ensure they could defeat the Ottoman, the Crusaders deployed nearly 25,000 soldiers, almost half of whom were cavalry, and 800 Hussite war wagons modeled after those from Bohemia.
At the same time, Hunyadi was given full command of this battle; neither the young king nor the papal envoy discreetly interfered, and even the Despot George Branković, who was usually fond of stirring up trouble, complied with Hunyadi's arrangements, generously allowing Serbian cavalry to appear on the battlefield.
In stark contrast to the well-prepared and confident Crusaders, the Ottoman camp was in disarray: Turahan Bey, extremely dissatisfied with Kasim Pasha's repeated defeats, forcibly took the only three thousand Sipahi cavalry available, claiming he would ambush near the swamps and, once the infidels arrived, charge the enemy with Ishak Bey and Anaftolu Pasha.
In response, Kasim Pasha, whose overall command had been split, could only comply and ordered his weak ten thousand militia to construct temporary fortifications, hoping to withstand the first wave of Christian attacks.
However, he had not even completed half of the fortifications when the 3rd arrived.
On the morning of this day, after confirming that the moving heads in the distance were enemy troops, Kasim Pasha, realizing his forces could not withstand the enemy cavalry, was forced to calm himself down and sent scouts to find the three reinforcements.
Nearly half an hour later, all he received was the bad news that they were still on their way.
"Where are Turahan Bey's reinforcements!?
"Where is Ishak Bey!?
"And Arnavutlu Iskender Pasha's troops!?
"Three commanders, why are you all just watching? Have you truly all betrayed us?" Upon learning that reinforcements would take at least two or three hours to arrive, the isolated and helpless adjutant exploded in frustration, clutching his head and roaring.
Kasim Pasha, a veteran of many battles, could only sigh and go to the front line, squinting to observe the enemy's formation.
"What is that?" Soon, as the enemy gradually approached, he felt a sudden sense of dread and was dumbfounded, "No, this is, this isn't, the Hussite war wagons of the Bohemian Slavs?
"Allah above, how did the Magyars get so many Hussite war wagons!? This can't be right!!!"
"Pasha, what should we do now?" another adjutant beside him asked in terror.
Kasim Pasha, with trembling lips, forced his subordinate soldiers to calm down,
"It's alright, calm down, hold the position. As long as the reinforcements of those three arrive, everything will be fine."
"Pasha, but the Magyars are already charging!" The dispatch scout rushed back to report, which instead broke the army's morale.
"Then fight!" Seeing the arrow on the string, Kasim Pasha had no choice but to bite the bullet and order the entire army to attack, relying on the fortifications to resist the enemy.
But he quickly regretted his rash decision.
Less than a quarter of an hour later, seeing the temporary fortifications as fragile as paper under the Hussite war wagons and the iron hooves of the Christian heavy cavalry, and the conscripts being sent flying everywhere, the Pasha's hands trembled, on the verge of tears,
"Why did things turn out this way…?"
When Turahan Bey, Ishak Bey Hranic, and Arnavutlu Iskender Pasha arrived on the battlefield with their respective Sipahi cavalry, they saw no friendly forces still fighting the enemy.
Only the Magyar army's more than 800 Hussite war wagons and over twenty thousand Crusaders, whose numbers were no less than theirs and who still had strength, were waiting for the enemy, ready to continue their advance.
"Shh, is it still too late to retreat now?"
This was the first sentence uttered by Turahan Bey, the first of the three cavalry reinforcements to arrive on the battlefield, upon seeing the current situation of being outnumbered.
What happened next was simple: since the three cavalry units neither managed to support Kasim Pasha's forces nor arrived on the battlefield simultaneously, they were quickly defeated one after another by the high-spirited Crusaders, who drove their war wagons and rode their warhorses.
After a day and night of one-sided pursuit, the Ottoman army abandoned ten thousand casualties and fled the battlefield in disarray.
Although all four generals eventually escaped, it was clear that the Ottoman Sultanate had now lost the ability to control South Serbia and even North Bulgaria.
However, at this time, no one noticed that Arnavutlu Iskender Pasha, who had been routed by the Crusaders, quietly changed his escape direction, abandoning most of his subordinates and taking only 500 Albanian mountaineers of his own ethnicity towards the westernmost territory of the Ottoman Sultanate in Rumelia—
Central Albania, conquered by the Ottoman Sultanate 23 years earlier.