As for why the Bosporus Army's main force gathered here, we have to go back to when the Bosporus Army's military conference in Tana concluded a while ago.
During the conference, Manuel decided that the army would ambush the Golden Horde army along the Don River's waterways.
After the conference, he did not rush to leave but lingered at the meeting site for some time, accompanied by a few trusted confidants, waiting for an acquaintance to arrive.
A few minutes later, the person indeed appeared as he had expected.
"Long time no see, Manuel. May Allah protect us." Gracio, a new Venetian noble and his old acquaintance, appeared with his usual smooth demeanor.
"No need for pleasantries," Manuel softly interrupted his polite words, getting straight to the point. "When we were discussing military affairs just now, you Venetians were waiting outside, weren't you? Also, if I'm not mistaken, Consul Lando sent you today, didn't he?"
Gracio bowed and nodded noncommittally, anticipating the other party's words.
Seeing that the Venetians readily admitted it, Manuel did not dwell on accusations but, as planned, shared an excellent scheme with Gracio. "Since we are discussing this on your Venetian territory, I had some precautions in mind. But now that things have come to this, you Venetians should uphold your credibility as merchants, right?"
"Manuel, please trust your allies. We should still have that level of trust, shouldn't we?" Gracio and his group were clearly not very pleased with Manuel's words.
"No, no, no," Caesar gestured with an open hand, a typical Roman monarch's cunning smile on his face. "It seems you have misunderstood my meaning. My suggestion is, given the current developments, why don't you genuinely sell relevant intelligence to the Golden Horde?"
"But it definitely can't be real, right?" Gracio immediately reacted, his smooth smile becoming even more cunning and perverse.
"Half-truths are more convincing and better protect your commercial reputation, aren't they?" The young Caesar dramatically waved his arm, extended his right hand, and offered an olive branch. "A pleasure to cooperate?"
The Venetians accepted his olive branch without much hesitation. "A pleasure to cooperate, Caesar."
Turning the clock back to the present—
Because the Golden Horde instinctively believed the intelligence sold by the Venetians without scrutiny, their own decisions were subtly influenced.
Therefore, during this march, the Golden Horde army mostly did not avoid the muddy and wet areas along the Don River but advanced directly along the river course without any precautions.
In contrast to the unprepared Tatars, the Bosporus Army, according to their Caesar's plan, set up their encampment in the lower reaches of the Don River.
After learning that the Tatars were indeed marching along the Don River and were unlikely to deviate, Manuel boldly set up an ambush at Kherestz, where the main tributaries of the Don River converged, patiently waiting for the Golden Horde army to fall into his trap.
The result was exactly as he had planned: the Tatars not only jumped in without hesitation, but their General even openly mocked the Romans' miscalculation on the spot, unaware that they themselves were making a grave mistake.
What happened next was much simpler: since the Golden Horde army was the one being ambushed, and due to hydrological and geographical constraints, most of them had dismounted and were unarmored, coupled with the fact that most of the soldiers were resting, they were completely caught off guard.
In contrast, the Romans, who had been waiting for a long time, in order to mitigate the terrain's impact, had very few cavalry and firearm units deployed where they shouldn't be, and even heavy infantry was scarce.
Most of them were elite soldiers in light armor for easy movement, and skirmishers with more flexible formations.
Under these circumstances, the Golden Horde army couldn't even form a defensive formation.
Some soldiers attempting to converge with allied troops were caught and cut down by agile Bosporus soldiers as they began to move in confusion.
If it weren't for the Tatars' almost innate bravery, they would have completely collapsed in less than fifteen minutes.
"Don't panic, the enemy doesn't outnumber us by much. Allah, protect the entire army..." Just as Mahmoud, the General, quickly mounted his warhorse, attempting to restore order with his superior and colleagues, a sturdy Bosporus officer suddenly appeared before him like a ghost, startling Mahmoud into immediately fleeing the area on horseback.
But the ground here was truly too soft; the warhorse only stomped a few steps before sinking into the mud, man and horse alike.
And this Tatar General was caught by the enemy, cut down with one stroke, and then had his head severed with another.
And this was just a microcosm of the Golden Horde army's defeat.
In just half an hour, except for the Golden Horde General, who gathered less than two thousand remnants, including civilians, and fled in panic towards Sarai, all other soldiers and able-bodied men were annihilated or captured by the Bosporus Army.
After the battle and once safety was confirmed, Manuel immediately ordered a statistical analysis of the battle's losses and gains.
The results pleasantly surprised him: the Bosporus Army, at the cost of less than a thousand casualties, captured at least five thousand enemy soldiers and herdsmen, and likely killed over a thousand enemies.
In other words, if nothing unexpected happened, the Golden Horde's power in the southern Eastern European Great Plains was just a step away from being completely wiped out, and he had directly stepped on the gas for the Khanate's complete collapse.
When Manuel informed his subordinates of this matter and the possible aftermath, these Generals became excited.
Even more so, some, like Tukharovsky, even incited their Caesar on the spot to march on Sarai and completely extinguish the heart of the Khanate.
Destroying this pagan regime that had rampaged across the Great Plains for several years was, in their eyes, boundless glory.
Even if they couldn't destroy this Tatar city, a simple round of plunder would be a significant return on investment.
However, to their surprise, their respected Caesar rejected this proposal; no matter how much they persuaded him, he showed no intention of attacking Sarai.
The most aggressive order Manuel issued was, at most, to have the army escort the captives back into the Autocratic State's territory, while specifically ordering Posadas to lead about a quarter of the Tauris Second Legion soldiers, the Tatar Legion, and half of the Philaka Legion soldiers to march along the river to the middle reaches of the Don River, burning and plundering all towns along the way, extensively looting spoils of war, and slaughtering any pagans encountered.
Later, when asked by his subordinates about the reason for his actions at the time, Manuel simply offered this analogy:
"Would you blow up a toilet just because it's full of filth?"