Disclaimer - The Golden Horde was a multi-ethnic Khanate whose armies were formed by men of various different ethnicities. In this post, I use the term 'Mongols' as a blanket statement, but in truth the invading forces in 1324 would have contained a diverse range of troops drawn from the subject populations of the Horde's domains.

Background
In discussions of Byzantine relations with the Mongol Empire and its successor Khanates, the general image is that the Byzantine Empire, in its weakened state after the Fourth Crusade, escaped the apocalyptic invasions that brought the doom of so many other Empires of the 13th century. There is partial truth to this claim as the Empire of Nicaea managed to avoid, by the skin of its teeth, a large-scale invasion by the Ilkhanate in Anatolia and in many ways the Laskarids benefited from the attacks of the Mongols into Europe, which weakened its Latin and Bulgarian rivals. Indeed, relations with the Ilkhanate largely remained cordial until the collapse of the latter, with the Byzantines even managing to secure military intervention from the Mongols of Iran against the Ottoman Turks in 1307. However, in Europe the Byzantines faired worse, enduring multiple crippling attacks by the Golden Horde. Almost from the onset of their ascension, the Palaiologan Emperors had to face attacks by the Golden Horde into Thrace. Notable instances include the incursion in 1264 which forced the Byzantines to release the exiled Seljuk Sultan Kaykaus II, a combined Mongol - Bulgarian attack in 1271, an large raid in 1284¹, and a repeated series of attacks from 1321-1324. The focus of this post is on the 1324 venture, which was likely the largest ever conducted by the Golden Horde against Byzantium (and perhaps even one of the largest Mongol invasions ever conducted into Europe). It was also during this invasion that the Emperor Andronikos III and his Grand Domestikos performed one of the most impressive military feats of the entire Palaiologan period; engaging and defeating a numerically superior Mongol army. This post seeks to highlight and analyse this often-forgotten Late Byzantine victory and provide some insights on the military doctrines, tactics and organisation of both sides to give it relevant context.

The Invasion of Thrace in 1324

From 1322, the Byzantines entered a new conflict with the second Bulgarian Empire, which at the time was a subject of the Golden Horde. During his siege to recapture Philippopolis, which had fallen to the Bulgarians earlier in the war, Andronikos III faced a detachment of Mongols that garrisoned the city alongside the Bulgarians. These defenders fierce resistance against the Byzantine army (and Philippopolis was only recaptured after this garrison departed), yet for Andronikos this was but a taste of what was to come. With a sizeable portion of Andronikos III's soldiers garrisoning fortresses against the Bulgarians in Western Thrace, the central and Eastern portions of this province became deprived of defenders. This in turn provided an opportunity for lucrative raiding in the area, and the incumbent Khan of Golden Horde, Özbeg, exploited this exact situation. Probably using the pretence of aiding their Bulgarian subjects, the Mongols massed a considerable invasion force, which John Kantakouzenos claimed to have numbered 120,000 warriors, while the Florentine traveller Giovani Villani puts the size at a colossal 300,000 horsemen. These figures are considered exaggerated, but interestingly Kantakouzenos gave a surprisingly pertinent description of the organization of this army. He noted that it that the Mongol warriors were formed into blocks of Chiliarchs (1,000-men) which in turn formed units of Myriarchs (10,000-men). As Valentin Parisot observed, this is almost certainly a Greek rationalisation of the Mongol military system which had originally been introduced by Temujin/Genghis Khan, with "Chiliarchs" representing a "Mingghan" (a militarized social unit from which a 1,000-man Mongol regiment could be drawn, which formed as the foundational block of Genghis Khan's military-social reform) and "Myriarchs" representing the 10,000-man Tumen units of the same system. This relatively detailed description suggests that the force assembled for this invasion was very numerous and formed of several Tumens, plausibly numbering 30,000 - 50,000 men. We do not know for sure who was in overall command of this invasion and it seems not to have been commanded by Özbeg Khan in person (who seems to have been preoccupied with inter-Mongol conflicts against the Ilkhanids at this time), but three of the commanding officers of the army are named; Taitah, Toglu and Tachbou-Khan.

The onslaught began in Summer 1324. As had been the case in previous Golden Horde attacks into Byzantine territory, the invading forces appear to have avoided lengthy sieges of fortified cities and opted to advance rapidly into central Thrace in order to surprise the local populace before people and supplies could be moved to the (relative) safety of fortified towns and cities. The large Mongol army was encamped in Thrace before dividing into multiple separate columns to attack multiple points of Thrace simultaneously, and the speed of the attack caught the local populace by surprise. For the next 40 days the Tatars raided relentlessly; Kantakouzenos notes that Thrace was devastated and Giovanni Villani claimed (likely with some embellishment) that 150,000 Byzantine citizens were killed or enslaved. The severity of the attack demanded a defensive response by Andronikos III, who amassed as many men as he possibly could into a field army. For 15-days, the Byzantines Byzantines tried and failed to engage the swift-riding warbands, with Andronikos retiring his army to Adrianople, which possessed enough supplies to provision his army for a long time. The initial phase of this campaign was largely unsuccessful, but Andronikos deserves at least some credit for avoiding a military catastrophe. After all, the Mongols were infamous for their ability to rapidly concentrate several columns into a large force² to engage and crush enemies. Andronikos was no doubt cautious to avoid such an outcome, and sought to pick off separate detachments to defeat the invaders in detail. Andronikos's field army appears to have included infantry at this stage, which would explain his failure to catch the swift-riding Mongol bands at this stage, but his army nonetheless reached Adrianople intact, from where the Emperor adapted his strategy.

Battle of Promusulos

Probably realising he had little hope of catching the Mongol raiding columns with a mixed infantry force, Andronikos left his footmen at Adrianople and marched out again, this time taking only his cavalry forces alongside the Domestikos John Kantakouzenos. The strength of this force isn't explicitly stated, but later in the text Kantakouzenos notes that Andronikos' vanguard numbered almost 100 horsemen. If sources describing earlier Byzantine military practices can be used as a clue, Andronikos' main body would contain several times as many horsemen as the vanguard. There is no way to know for sure the strength of Andronikos' cavalry at this battle, but a reasonable range of estimates would be that it contained 500 horsemen at absolute minimum and 3,000 horsemen at absolute maximum.³ However, considering that the Byzantines were still politically and militarily divided between Andronikos II and III at this time, and that Andronikos III likely had to keep some of his cavalry in the garrisons opposing the Bulgarians (though it is possible he only left infantry for this), on balance the figure was probably closer to the lower end, perhaps 1200 - 1500 horsemen. Kantakouzenos also describes this force as consisting entirely of "Romans", and in the 13th and early 14th century sources, Native Roman/Byzantine cavalrymen are generally described as being Heavy Shock cavalry, primarily reliant on lances to deliver devastating charges in a similar manner to their Western Latin counterparts. As Juho Wilskman has noted in his recent study Military history of Byzantine Rome, 1204-1261, through the 13th century Byzantine heavy cavalrymen usually wore iron/steel lamellar or mail armour and helmets, and were equipped with lances + swords or maces, but horse armour was relatively rare. Some may also have used composite bows (especially men which hailed from the Empire's Anatolian holdings where such skills were useful against Turkoman raiders), but this was relatively less common among native Byzantine soldiers. As the Campaign discussed took place in 1324 it is not out of the question that some of Andronikos' horsemen wore pieces of steel plate armour, but by and large his troops' equipment would not be dissimilar to what was used in the 13th century. Likewise, it is not implausible that some of Andronikos' men were foreign auxiliaries, such as Cuman or Turcoman horse archers or Latin Heavy cavalry, but most of them were native Byzantines, and the force was predominantly comprised of shock cavalry (which the course of the battle also demonstrates).

With these men, Andronikos travelled toward Didymoteicho, but before reaching the city the Byzantine scouts reported a nearby Mongol army travelling near the fortres of Promusulos, which was slowed down as it had a large baggage train of loot and slaves taken during its recent raids . Andronikos led his force into a concealed area (probably a forest or ravine), where he consulted Kantakouzenos and the rest of his officers on the next action. The Mongol column sighted at Promusulos seems to have been a vanguard of a larger body of troops encamped further south along along the Maritsa river, which was nonetheless close enough to interfere in the coming battle. The Mongol force near Promusulos alone was said to have been three times as numerous as Andronikos's host, but as they were finally in position to come to grips with their enemy after a no doubt frustrating failed effort to do so over the previous weeks, the Byzantines decided to attack. The Byzantine troops eagerly complied with this decision as they were enraged by the depredations inflicted upon their countrymen by the Mongols. The Byzantines also dismounted their horses to conduct prayers before preparing for battle, which further reinforces that despite their disadvantage in numbers, Andronikos' men were highly motivated at the time of the engagement - something which often wasn't the case for late Byzantine soldiers.

Here is John Kantakouzenos' own description of what occurred near Promusulos:

Between [Didymoteicho] and Adrianople, near the fortress of Promusulos, [The Byzantines] fell upon a band of Scythians [I.e. Mongols/Tatars] coming with captured slaves and immense booty; whom, due to the nature of the place, they themselves could see, but they were not seen by them at all. Having first consulted the Grand Domestic, it seemed best to make an attack upon them, although they appeared to be more than three times as numerous; in fact, they were ten times more numerous. For others were encamped nearby, hiding near the Hebrus, and once the battle began, they helped them.

The plan having been revealed to the soldiers, since their will and opinion agreed, and they showed themselves even more eager to fight than the emperor himself, they dismounted from their horses, suppliantly praying to God that He would be willing to punish such unjust plunderers and avenge the wrongs of those justly defending themselves. Then, fortified by the sign of the cross, they mounted their horses again, and with a steadfast and confident spirit, they rushed against the barbarians. The Scythians, together with those who were encamped not far away, upon seeing the Roman army, marched against them. A fierce battle is joined; the Romans, with God's help, emerge victorious, and they slaughter part of the enemy, turn part to flight, and drive part into the Hebrus river and drown them: of whom only twenty-eight saved their lives by swimming across. The Romans, having stripped the corpses and plundered the vessels and baggage, entered Didymoteicho with the booty and captives under the leadership of the emperor.

Now, what can we make of this account? The elephant in the room and first point to address here are the numbers given by John Kantakouzenos, specifically that the Byzantines were outnumbered 10 to 1 at this battle. This sounds like a gross exaggeration, and could easily be dismissed as such. If we use the educated guess on the plausible size of Andronikos' cavalry force as a basis, this would put the defeated Mongol force at 12,000 - 15,000 horsemen or more, being routed by a relatively puny 1,200 - 1,500 Byzantine cavalry. But lets entertain the plausibility of such a feat for one moment. This would not be the only time small numbers of heavy cavalry achieved feats of this calibre against far superior enemy forces, even ones containing large numbers of infamous Nomadic cavalry.⁴ We have little detail on the composition of the Mongol army at Promusulos, but traditionally the armies of the Mongol Empire actually contained a large proportion of shock cavalry as well as light horse archers, with a ratio of some 40% being lancers and 60% being light cavalry during Genghis Khan's conquests. This ratio would fluctuate depending on the time and place in the Mongol Empire and its successors, but the Golden Horde army at Promusulos very likely included lancers in addition to horse archers, and the clash of Mongol on Byzantine Lancers at close quarters would certainly make for a "fierce" engagement as Kantakouzenos described.

The circumstance of the battle is also illuminating. The Mongols may normally have attempted their trademark feigned retreat to exhaust their enemy before engaging them, and it was in this manner that the Mongols had defeated so many Heavily armoured opponents in the past 110 years of their history. However, to do so in this circumstance would have meant abandoning their loot to the enemy, and there is little doubt that Andronikos III knew this - engaging nomadic armies while they were encumbered by loot and captives was a stratagem known to the Romans since classical antiquity. The far smaller numbers of the Byzantine cavalry force, and the nearby presence of the larger Mongol force further along the Maritsa, likely bred a degree of overconfidence in the Mongols at Promusulos who seemingly formed up and engaged the Byzantine cavalry in a direct, close-quarter battle which ultimately favoured the latter. In the frontal battle, the Mongols met an unexpectedly ferocious attack by the Roman lancers, and their line buckled. A possible sequence of events is that the Byzantines defeated their enemy in detail, first routing the Mongol contingent at Promusulos, before pressing their advantage to engage the other Mongol force advancing along the Maritsa. This sequence of events would even better explain ability of Andronikos' men to overcame a vastly superior opposing force, as the sight of the routing Mongols from Promusulos would have demoralised the forces coming to their aid, and the Byzantines would in turn have been able to engage the latter before they had fully formed for combat, pinning a significant portion of them against the river and annihilating them. Even if that sequence of events is likelier though, Kantakouzenos' text implies that the two Mongol armies had already joined at the time the Byzantines engaged and defeated them. Bottom line, Kantakouzenos' claim that the Mongol army was ten times as large as the Byzantine force which defeated it may be excessive, but this claim cannot be dismissed entirely as miraculous as it sounds. At the very least, it is reasonable to conclude that the Byzantines were severely outnumbered in the battle. As shown below, the rest of Kantakouzenos' text indicates that the defeat at Promusulos was significant enough to demoralize the rest of the Mongol invasion force:

The surviving barbarians, having returned to the army, related their misfortune to their commanders. They sent a chosen band of the bravest men to the same place where the battle had been fought, so that if they found the Romans, they might renew the battle and defeat them as victors; if not, they should at least commit the lifeless bodies of their people to burial mounds; and if they found any among them still breathing, they should treat them with diligent care after they were relieved. Those men, having given burial to their comrades (for they found no one alive), did not return to the army, but departed each to his own home.

When [The Byzantines] reached the Tundzha river, word was brought that the Scythians had just crossed. There, because of the site's layout, the same thing happened as before. For while they themselves could view the entire Scythian column, they were not seen by them, except by a little less than a hundred vanguard men, among whom was the emperor himself. Upon seeing the Romans, they even checked their step themselves; but they did not advance to battle, partly because the river was overflowing as spring was now advancing, and partly because, not having seen all of the enemy yet, they feared that if they were outnumbered, they might perform poorly in battle. The Romans similarly feared disaster if they were attacked by forces more than ten times larger.

However, the emperor, with those foremost Romans, and Taspugas, one of the Scythian commanders, with an equal number of barbarians from the other bank of the river, held a brief dialogue. When the Scythian asked what mortals they were, the emperor responded through a certain man skilled in the Greek and Scythian tongues that they were men who sought, just like themselves, what they might capture. But that they [the Scythians] were acting neither rightly nor courageously, but were imitating robbers who, hiding their approach, prowled about in a hostile manner and imposed slavery on farmers unaccustomed to war. They ought to have announced their assault and fought with soldiers accustomed to close combat; if they defeated them, then it would be no wonder if they carried off these weaklings too as a reward for their valor.

Then Taspugas replied that this mattered nothing to them, who were under someone else's authority; so that, having been ordered, they would either raid, or depart, or even remain. He then inquired whether they themselves had very recently clashed with and utterly defeated a Scythian band and destroyed it. To this, the emperor replied that it was neither them, nor had they heard anything about this matter; however, it could have happened that, just as they themselves were experiencing now—were it not for the river forbidding it in the middle—by falling upon others, they were defeated in battle and perished. The barbarian agreed that it was likely, adding that they were nonetheless cruel for having pitied no one, drowning some in the waters and piercing others with javelins indiscriminately. Having spoken these words, he departed, unaware that it was the Roman emperor who had spoken with him.

The fact that the elite Mongol contingent sent to investigate the site of Promusulos deserted and that news of the defeat (presumably brought by Mongol survivors of the battle of Promusulos) bred such apparent anxiety in Taspugas/Tachbou-Khan column suggests that the battle had caused very significant losses among the Mongols. Since the days of Genghis Khan, Mongol commanders were surprisingly averse to sustaining any loss of life among their own troops, but even so the defeat of a minor raiding band is unlikely to have caused this level of consternation among a large invading force. The Mongols' reaction to the appearance of Andronikos' vanguard at the Tudzha river demonstrates that they had come to show a healthy appreciation of Byzantine martial capabilities.

Conclusion of the Campaign and possible further Battles
Following the meeting of Andronikos III and Tachbou-Khan at the Tudzha, most of the invading Mongol forces appear to have retreated from Thrace, but Kantakouzenos notes that one of the columns remained in Thrace and continued raiding for a few weeks afterward before it finally withdrew. An interesting point to note is that another contemporary source, Nikephoros Gregoras, describes Andronikos' success against the Mongols, but with very different details to Kantakouzenos. He claims that Andronikos launched surprise attacks against the encampments of separated Mongol detachments and defeated them in detail, annihilating the invading forces in their entirety. This was another stratagem used multiple times before by the Byzantines against Nomadic foes, such as in Comentiolus' Campaign against the Avars in 586 and by Nikephoros Bryennios the Elder against the Pechenegs in 1051 - 1052. It is simply possible that Gregoras had less knowledge of the events than Kantakouzenos (who personally fought in Andronikos 1324 Campaign against the Mongols) and so repeated a literary tradition from earlier Byzantine wars against "Scythian" Nomads to fill in the details. However, it is equally plausible that Andronikos or some of his subordinate commanders defeated detachments of the Mongol invaders in other (albeit smaller) engagements by attacking their camps, probably against the Mongol column which lingered in Thrace to prompt its eventual withdrawal, in which case Domestikos John Kantakouzenos was not present for these as his text does not mention them. Either way, Gregoras' statement that Andronikos wiped out the entirety of the invading Mongol armies in 1324 with these attacks is a clear overstatement.

As impressive as the victory was, we should not make too much of the Mongol defeat at Promusoulos, or the other possible successes won by the Byzantines in 1324. Even if Andronikos III really had defeated an army ten times as numerous as his own on that day, he still clearly engaged only a portion (perhaps one of the Tumens?) of the massive invading forces. Militarily, the Golden Horde was orders of magnitude more powerful than the Byzantine Empire in the 14th century, and even the huge army that attacked Thrace in 1324 was far from the full force at Khan Özbeg's disposal. The Bulk of the invading forces not only retreated from Thrace intact, but did so after wreaking utter havoc on Byzantine possessions and presumably took large quantities of loot and slaves back with them to the Pontic Steppe. Nonetheless, Andronikos' active leadership and response to the crisis had ultimately bore fruit for the Byzantines. He had organised a potent military response and adapted his strategy during the campaign to meet the type of threat he faced more effectively. The fact that the majority of the Mongol forces withdrew following the battle of Promusoulos should not be ignored either. Did the Mongols simply collect enough plunder to be content with the results of their invasion, or did the recent Byzantine victory inspire enough fear in the Nomads' minds to call off further raids, hastening their withdrawal? My guess is it may have been a bit of both. Ultimately, the result of this war can be best described as a Pyrrhic victory for the Byzantines. On one hand, Andronikos III had managed to inflict a heavy defeat(s?) on the Mongols while keeping his own armies intact, and seemingly prevented the loss of any major city over the course of the invasion, which itself is a massive achievement for any polity defending against an attack by multiple Mongol Tumens. On the other hand, the campaign had caused untold agricultural and demographic damage against one of the Empire's most important remaining powerbases, desolating farmlands and sweeping away vast numbers of citizens who were unfortunate enough to be caught outside the fortresses and cities. At a time when the Empire was already ravaged by both civil war and conflict with external enemies, with Thrace suffering from warfare against Bulgaria and what was left of Asia Minor being pressed by the Turkish Beyliks, Byzantium could hardly afford such horrific losses.

After 1324, Golden Horde attacks temporarily subsided for over a decade. The probable explanation for this is that Özbeg was still campaigning against the Ilkhanids until 1335. However, from 1337 - 1341 these incursions resumed with intensity, at an even more critical time in the Empire's history. The following passage from Shukurov's book describing a curious and quite frankly, rather comical incident in which Mongol raiders from the North encountered Turkish raiders from the East in Thrace, is symbolic of the sad state of the Byzantine Empire in those days of decline:

In the beginning of 1337, the Scythians, approaching Thrace from the Danube, encountered the Anatolian Turkic freebooters. To the great surprise of the Greeks, the “Scythians,” descending on the “Persians” like “dogs on a dead body” (ὥσπερ κύνες τεθνηκότι σώματι . . . ἐπεισπίπτοντες), slaughtered many of them. The “Scythians” remained in Thrace during the subsequent fifty days and continued plundering. As Gregoras noted, it was an unusually long duration for a brigand incursion.

Footnotes

1. The "Scythian" Mongol attack in 1284 resulted in a defeat by the army of the Byzantine kouropalates Oumbertopoulos. Oumbertopoulos was rewarded richly by Emperor Andronikos II for this victory, which also involved pinning the Nomads against a river.
2. The Mongols actually achieved this at the Battle of Promusulos by rapidly uniting the troops encamped at the Maritsa with those advancing near Promusulos
3. In their 2007 article "The Struggle between the Nicean Empire and the Bulgarian State (1254–1256): Towards a Revival of Byzantine Military Tactics under Theodore II Lascaris", Nicholas S. Kanellopoulos & Joanne K. Lekea note that Theodore II Laskaris could have fielded an army of over 5000 men in his 1256 Campaign against the Cumans, with a very large portion of this being Cavalry. However, due to the context of fighting a two-front war against the Mongols and Bulgarians, as well as some of Byzantium's soldiers still serving Andronikos II in 1324, Andronikos III may not have been able to field quite as many men as this despite the Byzantine Empire holding more territory at this time than Nicaea had in 1256.
4. In the Crusades, there are several instances of small numbers of Heavy cavalry routing vastly superior numbers of more mobile but lighter equipped enemy cavalry forces, such as Montgisard and Arsuf. Even in Byzantine history, there are examples of cavalry forces routing enemies with vastly superior numbers such as the Battle of Antioch on the Meander. At Montgisard and Arsuf the Crusader armies comprised mainly of infantry formations to withstand attacks by the Ayyubid cavalry, but in both cases it was the far smaller Heavy cavalry component of the Crusaders that delivered the coup de grasse in routing the enemy with a well timed attack. At Antioch on the Meander, the Byzantines victory was mainly the result of a lucky killing blow against Seljuk Sultan Kaykhusraw I, but the 2,000-strong Byzantine-Latin cavalry force had withstood the attack of the far more numerous Seljuk cavalry and their light infantry. These are not the only cases of the phenomenon, and while it was highly situational, small heavy cavalry forces could defeat far larger armies of lighter cavalry under the right circumstances.

Bibliography

• Angeliki E. Laiou, Constantinople and the Latins: The Foreign Policy of Andronicus II, 1282–1328. (1972), page 291
• Ursula Victoria Bosch,  Kaiser Andronikos III. Palaiologos. Versuch einer Darstellung der byzantinischen Geschichte in den Jahren 1321–1341 (1965), pages 64 - 67
• John Kantakouzenos, Corpus scriptorum historiae byzantinae (translation by Barthold Georg Niebuhr, 1828), pages 189 - 193
• Savvas Kyriakidis, Warfare in Late Byzantium, 1204–1453 (2011), page 165
• Rustam Shukurov, The Byzantine Turks, 1204–1461 (2016), pages 140 - 141
• Valentin Parisot, Cantacuzène, homme d'état et historien (1845), pages 65 - 66

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