Battle of Rusokastro

After the death of the Bulgarian tsar Michael III Shishman, which occurred before 1331, the political situation in Bulgaria proved to be extremely unstable. This period of disorder and internal struggles was skillfully exploited by the Byzantine emperor Andronikos III, who not only failed to fulfill his allied obligations to Michael III Shishman during the war against Serbia in 1330 but also undertook aggressive actions against Bulgarian territories.

Taking advantage of the chaos in Bulgaria, Andronikos III seized a significant area between Yambol and the Black Sea. This territory included several important cities such as Yambol, Rosokastro, Ktenia, located near the present-day village of Lozarevo in the Karnobat region, and Aetos, known today as Aytos. Furthermore, the Byzantine emperor managed to capture key ports along the Bulgarian Black Sea coast – Mesembria and Anchialos. These ports were particularly important as they had been the subject of a long-standing dispute between Bulgarians and Byzantines due to their strategic significance for trade and naval operations in the region.

At this critical moment of political crisis in Bulgaria, Ivan Alexander ascended the throne in Tarnovo. He recognized the necessity to restore control over the cities taken by Byzantium and to stabilize the state. Therefore, as early as the spring of 1331, he launched a campaign against Byzantium with the aim of reclaiming the lost territories in Thrace.

According to the accounts of the Byzantine chronicler Kantakouzenos, Ivan Alexander gathered all the troops available among the Mizians – the Bulgarian population in the northeastern lands – and added a significant number of allied Scythian (Tatar) warriors. This allied support was crucial for the success of the campaign. An interesting fact is that some of the cities Ivan Alexander aimed to recover had voluntarily surrendered to the Byzantine emperor, while others were subdued by force. The campaign was not directed against cities that had been firmly opposed to Byzantine rule but rather against those that had shifted their loyalty in favor of Andronikos III.

At the same time, Andronikos III was engaged in fighting the Turks in Asia Minor in 1331, which prevented him from effectively opposing the Bulgarian campaign. This situation gave Ivan Alexander the opportunity to act without serious Byzantine resistance and to restore Bulgarian control over important territories.

In addition to military actions against Byzantium, Ivan Alexander undertook diplomatic steps to strengthen his position. He established friendly relations with the Serbian ruler Stefan Dušan, who ascended the throne on September 8, 1331. Stefan Dušan sought rapprochement with Bulgaria to consolidate his power, and Ivan Alexander, threatened by Byzantium, found it advantageous to improve relations with Serbia. This mutual benefit led to the conclusion of a lasting agreement, sealed by marriage – Ivan Alexander's sister, Elena, married Stefan Dušan.

This alliance with Serbia secured Ivan Alexander a stable rear from the west, allowing him to focus on the struggle against Byzantium and to count on success in the forthcoming military actions. Thus, at the beginning of 1331, Bulgaria began to regain its territorial integrity and political stability after the period of crisis caused by the death of Michael III Shishman and Byzantine aggression.

In the summer of 1332, the Byzantine Emperor Andronikos III decided to undertake an undeclared and unexpected war against the Bulgarians. This sudden aggression was aimed at seizing the fortresses around Hemus, which had recently come under the rule of the Bulgarian Tsar Ivan Alexander. These fortresses held strategic importance as they were located in the area of the Balkan range, known in some sources as Hemus, and controlling them would have provided Byzantium with better access and influence over the northern Bulgarian territories.

Andronikos III gathered sufficient troops and invaded Bulgarian territory, with the Byzantine forces beginning to ravage and burn the enemy lands. Their treatment of the grain stored on the threshing floors was particularly harsh; it was not spared but destroyed in order to deprive the Bulgarian population of food and resources. This campaign took place in the Balkan range area, which confirms the interpretation of Hemus as precisely this mountain chain.

According to some sources, the battle of Rusokastro took place as early as 1331, with Andronikos III managing to conquer several Bulgarian towns in the spring of that year. These conquests were almost unopposed, with only the town of Anchialos remaining unconquered. The reason for the lack of serious resistance was that Tsar Ivan Alexander was occupied with suppressing a rebellion organized by his uncle Belaur. This rebellion covered the region around the town of Vidin and the valleys of the Timok and Morava rivers, diverting the attention and resources of the Bulgarian ruler.

Initially, Ivan Alexander attempted to resolve the conflict diplomatically by starting negotiations with Andronikos III in order to persuade him to withdraw and return the conquered towns. Despite his efforts, the Byzantine emperor refused to retreat, forcing the Bulgarian tsar to undertake military actions.

To oppose the Byzantine aggression, Ivan Alexander gathered about 8,000 soldiers, according to the chronicler Nikephoros Gregoras. To these forces joined 2,000 Nemian Scythians, also known as Tatars, who further strengthened the Bulgarian army. The tsar set out from the capital Tarnovo and after five days’ march reached a certain location not specified in the sources but presumed to be a strategically important point for the upcoming battle.

The passage of the Bulgarian troops likely took the safest and shortest route from Tarnovgrad through Veliki Preslav. From there, the army passed through the fortress of Ovchaga, also known as Asparuhovo, then continued through the Aytos Pass to the town of Aetos (modern Aytos). From Aetos, there was a road leading to Rusokastro, Develt (modern Debelt), Skopel (Eskipolos), Vrizis (Bunarhisar), Visa, and even Constantinople. It is probable that the Byzantine army also used this route during its advance into Bulgarian lands, making the area around Rusokastro key for the forthcoming battle and control over the region.

The distance between the capital of the Second Bulgarian Empire, Tarnovgrad, and the site of the battle at Rusokastro, known as Rosokastro, is approximately 260–270 kilometers along the indicated route. At the same time, the distance from Tarnovgrad to Aetos, where the Bulgarian army established its camp, is slightly shorter—about 230–240 kilometers. This difference in distances is significant for understanding the military movements and logistics of the Bulgarian army prior to the engagement.

According to the accounts of the Byzantine chronicler John Kantakouzenos, the Bulgarian army encamped at Aetos. This location was chosen deliberately, as Aytos is a strategically important town situated at the entrance of the pass in the Balkan range. Through this pass runs a road connecting the mountainous regions with Provadia, making control over Aetos crucial for the movement of troops and supplies.

The movement of the Bulgarian army to Aetos was accompanied by varying rates of advance depending on the type of troops. The Bulgarian cavalry, which likely formed the vanguard of the army, could cover the distance to Aetos in about five days. This rapid movement was essential for executing surprise maneuvers and establishing control over key points. On the other hand, the infantry required about ten days to reach the same location, necessitating more prolonged planning and coordination among the different units of the army.

In order to establish the Bulgarian army’s camp near the fortress of Aetos, the troops first took control of the fortress itself. This was an important tactical move, as the fortress blocked access from the Aytos pass to the plain, and controlling it provided a protected rear and the ability to observe enemy movements. Although it is unlikely that the fortress was captured by the mounted vanguard alone, it is more probable that the local Bulgarian population allowed the troops into the fortress, indicating popular support and solidarity with the Bulgarian cause.

An interesting fact is that the chronicles of Grigora and Kantakouzenos do not provide information about the behavior of the garrison and the population of Aetos during these events. This leaves room for speculation that the garrison was either defeated or fled, while the local population chose to assist the Bulgarian forces, which facilitated the occupation of the fortress.

The fortress of Aetos, visited by the Czech historian Konstantin Jireček at the end of the 19th century, is located on Hisarbar Hill, which rises 185 meters above the town. It is situated on the northwestern side of Aytos and represents a fortification with an irregular triangular shape. The triangle is wider to the south and narrows toward the north with an acute angle. The length of the fortification is about 300 paces, and the remains of the fortress lie on the hilltop, which is surrounded by steep slopes on all sides, making it naturally defensible.

Within the fortress are the foundations of three towers, the largest of which is located at the highest point in the middle of the fortress. Archaeological excavations also reveal that the town had a second fortress with walls about two meters thick, topped with round towers, attesting to the importance of this site as a military and administrative center.

The occupation of the fortress of Aetos by the Bulgarian army was a key moment in the preparations for the battle at Rusokastro, as control over it provided a strategic advantage and prevented enemy forces from using the pass to advance toward the plain. This action demonstrates the well-considered tactics and coordination of the Bulgarian command under Tsar Ivan Alexander and his military leaders.

On the road between Aetos and Rosokastro there was a strategically important pass that played a key role in the upcoming military actions. This pass, likely located in the area of the village of Vratitsa, was naturally fortified and further protected by a fortress erected there. The Bulgarian troops, under the command of Tsar Ivan Alexander, managed to occupy this pass, turning it into a strong defensive position. The defense of the passage was entrusted to an infantry detachment, which with determination and discipline did not allow the enemy to break through their lines.

The Roman (Byzantine) forces, led by Emperor Andronikos III, launched an offensive towards the narrow pass but encountered fierce resistance. Despite their efforts, the Byzantines failed to overcome the Bulgarian defense and were forced to retreat back to their camp. Their second assault on the pass also ended unsuccessfully, as they were again repelled and withdrew to their camp. These unsuccessful attempts demonstrate how well prepared the Bulgarians were and how important this position was for their defensive strategy.

After these failed attacks, negotiations began between the two sides. Despite the formal nature of the talks, both Bulgarians and Romans sought to outwit their opponent, using diplomatic tactics to their advantage. Tsar Ivan Alexander, realizing that reinforcements in the form of hired Tatar troops would soon arrive, deliberately prolonged the negotiations to buy time and strengthen his positions. According to the chronicle of Kantakouzenos, the negotiations concluded on 17 July 1332 with an agreement between the two rulers, but already the next day military actions resumed.

On the night of 17 to 18 July, 2,000 Tatar mercenaries arrived to Tsar Ivan Alexander, significantly increasing the size of the Bulgarian army. The total number of the Bulgarian ruler’s troops reached about 10,000, giving him a considerable advantage over the Roman army. According to the chronicler Grigora, Emperor Andronikos III had only 3,000 men, but this figure is probably understated to diminish the Bulgarian victory. From Kantakouzenos’s text it becomes clear that Andronikos III had been preparing for a campaign against the Bulgarians for a long time and had the opportunity to gather a larger army, but for unknown reasons did not do so.

Although the Roman scouts timely informed the emperor about the Bulgarian advance, Andronikos III led his army out of the camp and arranged it in battle order in the open, without seeking shelter in the nearby fortress of Rosokastro. This move shows either confidence in his forces or an underestimation of the Bulgarian army and its allies. This choice of position and tactics had a decisive impact on the course of the battle, which will be examined in the following parts of the narrative.

On the eve of the battle of Rusokastro, the Byzantine Emperor Andronikos III chose a strategic location for the deployment of his army. According to the chronicler Nikephoros Gregoras, the Roman (Byzantine) forces were positioned not far from the fortress of Rusokastro, with the main reason for this choice being the desire to have a secure refuge in case of a possible retreat. This refuge turned out to be the fortress itself, which was nearby and could provide protection and support in the event of an unfavorable development of the battle.

The most suitable place for the deployment of the Roman army proved to be the height known as the Great Mound, located about 4 kilometers north of the fortress of Rusokastro. This height held a commanding position over the entire surrounding area, which gave the Romans a significant tactical advantage. The flanks of the Great Mound were partially protected by the Rusokastrenska and Chakarlijska rivers, which further strengthened the positions of the Byzantine army and complicated any potential flanking maneuvers by the enemy.

The Great Mound has an elliptical shape, which allowed the Roman commanders to form a battle line in the shape of a crescent moon, with the horns of this crescent directed towards the fortress of Rusokastro. This specific battle formation is mentioned in the sources and represents an important element of the tactical preparation of the Roman army. In this way, the troops were arranged so that they could defend themselves effectively and use the terrain to their advantage.

On the other hand, the Bulgarian forces were likely deployed on the slope descending northward from the Great Mound. This slope represents the reverse peak of the height and provided an opportunity to conceal the Tatar cavalry behind it before it intervened in the battle. This tactic of concealment and sudden cavalry intervention was an important element of the Bulgarian battle strategy and could have a decisive influence on the course of the engagement.

There are two versions regarding the battle formation of the Byzantine army, with Nikephoros Gregoras stating that the emperor’s initial plan was to divide the army into three parts: a center and two wings. This classical distribution model allowed flexibility and the possibility of maneuvering during the battle.

However, when the emperor saw that the enemies were advancing, the Roman army extended its right and left wings into a long battle line, with heavily armed troops placed in the middle of this extended formation. The Byzantine army also had an arrière-garde in depth, which served as a strong support and reserve force.

Yet the fear of encirclement of the Roman troops prompted the emperor to immediately change his plan. He gathered the army into a double battle line, which took the shape of a crescent moon. This change in tactics aimed to provide better protection for the flanks and to prevent the danger of encirclement, while simultaneously preserving the possibility of a counterattack.

Thus deployed and organized, the Roman troops awaited the advance of the Bulgarian army, using the advantages of the terrain and the modified battle formation to oppose the enemy at Rusokastro. This episode of the battle illustrates the careful planning and adaptability of the Byzantine command under the conditions of dynamic medieval military art.

John Kantakouzenos provides important information regarding the arrangement of the Byzantine battle formation during the Battle of Rusokastro. He describes the army as consisting of a total of 16 phalanxes, distributed in two battle lines.

In the first line, there were 6 phalanxes arranged in a central part and two wings. The center of this first line was under the command of Emperor Andronikos III himself, which emphasizes the key role of this position.

The right wing was entrusted to the megas papias Tsamblakon, and the left wing to the protostrator, indicating that the leadership was distributed among senior military officials with different titles and responsibilities.

The second battle line included 10 phalanxes, each led by an experienced strategos, a high-ranking military commander. These details do not exclude each other but rather complement one another, as the second line occupied a wider front than the first, probably to cover a larger territory and provide greater flexibility during the battle.

At the decisive moment of the battle of Rusokastro, the two armies clashed face to face, with the initiative entirely in the hands of the Bulgarians. Their offensive tactics and determination allowed the Tatar units to penetrate the rear of the second Roman battle line, which caused complete chaos among the Roman ranks. The second battle line, surprised and threatened by the sudden strike, was forced to turn and flee, and the Tatars did not cease their pursuit all the way to the fortress of Rusokastro.

The first Roman battle line, although initially resisting the Bulgarian pressure stubbornly, also could not hold and was threatened from the rear. According to the chronicle of Grigora, the Roman soldiers noticed that the enemies were striving to seize the heights before them in order to outflank and attack them from behind. At that moment, they turned back and quickly fled into the fortress, seeking refuge behind its walls.

The inhabitants of the fortress, witnesses to the severe defeat of the Roman troops, fell into fear of the advancing Bulgarian ruler Alexander. In panic, they locked the gates of the fortress, hoping to save themselves from the approaching enemy. Nevertheless, the Bulgarians forcibly broke down the gates and stormed inside, driving out some of the inhabitants and killing others who were considered enemies. After capturing the fortress, the Bulgarians reinforced its walls to hold the conquered position.

The fortress of Rusokastro was exceptionally strong and strategically located on the rocky massif known as the Great Stone or Rusin Stone, situated north of the village of Rusokastro. This massif was distinguished by almost vertical slopes on the east, north, and south sides, which appear to have been artificially scarped to hinder enemy access. Below the northern and eastern slopes flows the relatively full-flowing Rosokastrenska River, which further complicated the siege of the fortress.

The height of the rocky cliffs reached about 80 meters, and the elevation of the hill was around 100 meters above sea level. The summit of the hill was accessible only from the west, which made the fortress easy to defend. It lay on the important road connecting Drastar, Pliska, Great Preslav, Aetos, Debelt, Fakia, Skopel (Eskipolos), Viza, and Constantinople, making it key for controlling the region.

According to the research of B. Dimitrov, the fortress wall followed the natural configuration of the terrain and enclosed an area of 15 to 20 decares (1.5 to 2 hectares). It was built from local quarried stone, bonded with white mortar mixed with small pieces of bricks, which provided strength and durability. The gate of the fortress was located on its western side, where P. Deligradev discovered traces of a defensive tower, probably intended to protect the entrance.

Access to the gate was along a narrow rocky strip, which was scarped on both sides and blocked by a moat, creating an additional barrier against attackers. In the western high part of the hill, near the gate, a second inner fortification was built—the citadel of the fortress, occupying an area of about 1 decare (0.1 hectare) and serving as the last line of defense.

These fortifications and the natural features of the terrain made the fortress of Rusokastro extremely difficult to capture, which explains why the Roman troops felt relatively safe inside it despite the heavy defeat on the battlefield. Nevertheless, the Bulgarian army managed to break through the defenses and seize the fortress, which was a significant success in the course of the battle and contributed to the final defeat of the Roman forces.

The battle of Rusokastro began at dawn, when the first rays of the sun had just started to illuminate the battlefield. Although it was fiercely fought, it was brief and ended around 8 o'clock in the morning, meaning it lasted no more than three and a half hours. This relatively short duration indicates the rapid development of events and the decisive nature of the fight.

The historians Grigora and John Kantakouzenos describe the beginning of the battle as a period of stubborn resistance by the Roman (Byzantine) troops. According to their accounts, the Byzantines fought fiercely, trying to hold their positions. However, modern researchers consider these claims unlikely, as other evidence suggests that the resistance was neither as prolonged nor as intense as the chroniclers describe.

John Kantakouzenos reports that the losses on both sides in the battle were minimal. According to his information, 37 horsemen and 65 infantrymen from the Roman army were captured or killed. Nevertheless, these figures are not convincing, and the actual losses on both sides were probably greater, since the short and intense battle would have resulted in more serious casualties.

A particularly important moment in the course of the battle was the capture or death of almost all the Tatar allies of the Romans, as Kantakouzenos claims. This loss caused confusion in the rear of the Byzantines, leading to the disruption of their battle order. It was this confusion that was the main reason for the beginning of the flight of the Roman troops, who could no longer withstand the pressure of the Bulgarian army.

After the battle, the Romans retreated to the fortress of Rusokastro, but there they could not withstand a prolonged siege. The main problems of the defenders were the lack of a water source, shortage of provisions for the people, and fodder for the livestock. These conditions seriously limited the possibilities for prolonged defense and maintenance of the army in the fortress.

Moreover, the Byzantines could not receive help from outside. The city of Anchialos (modern Pomorie) was already in Bulgarian hands, and Mesembria (modern Nesebar) was unable to provide support, as the circumstances around it were unfavorable and it was probably isolated or occupied with other tasks. This lack of support further weakened the Roman position and hastened the fall of Rusokastro.