Byzantine–Bulgarian Wars: Constantine V's Campaigns vs Constantine V's Bulgarian Campaigns (756–775)

The Byzantine war doctrine, due to the heavy and professional structure of its forces, was relatively static. It adhered to a fixed strategy and sought planned battles with a heavy infantry/cavalry combination. The Bulgarians, on the other hand, were a perfect example of asymmetric flexibility. They adapted instantly to changing conditions, shifting from raiding tactics to pitched battles (Telets era), and from pitched battles to guerrilla warfare (Telerig era). Telerig's post-defeat decision to abandon conventional warfare and hunt down agents, shifting the war's dimension to intelligence, demonstrates a high adaptability and an unexpected response capability. However, this flexibility was not sufficient to change the overall strategic situation.

The Bulgarians quickly adapted to changing war conditions, using hit-and-run tactics, feigned retreats, and ambushes instead of static defense. The Byzantine army remained doctrinally rigid, focusing mainly on pitched battles. However, Constantine V learned from failures and intensified his campaigns.

Attrition War

Attrition War

Constantine V clearly defined the center of gravity as the survival capability of the Bulgarian state. His goal was not to capture the capital or annex territory but to draw their armies into a field battle and annihilate them, neutralizing Bulgaria as a threat. He achieved exactly this at Anchialus, securing a crushing victory. In contrast, the Bulgarians correctly placed their Schwerpunkt on the Balkan passes. The success at Rishki was a product of this. However, Telets made a fatal mistake by abandoning this doctrine and dragging his army into a pitched battle. Strategically, it was the Byzantine side that correctly identified and persistently targeted the center of gravity.

Constantine V identified the seizure of the enemy capital Pliska as the center of gravity. However, he could not deliver the main blow because he was unable to cross the Balkan passes. The Bulgarians placed their resistance center on natural defensive lines and achieved asymmetric success by targeting Byzantine logistical vulnerabilities.

Ruse and intelligence supremacy turned the campaigns into a chess game in the information dimension. Constantine V generally tried to achieve tactical surprise by launching his campaigns with good operational security. However, the greatest military deception and intelligence victory of the Bulgarian side was Telerig's grand disinformation operation in 774. By deceiving the emperor with a fake defection request, he obtained the list of all Byzantine agents in Bulgaria and executed them in a comprehensive purge. This counter-intelligence strike collapsed a decade-old Byzantine intelligence network overnight. This event demonstrated that deception and intelligence superiority could be more effective than battle.

Telerig's operation to expose Byzantine agents is a classic counter-intelligence lesson. This deception blinded Byzantium and caught Constantine V unprepared for his final campaign. Although the Byzantines attempted to interfere in Bulgarian internal politics, they could not achieve a deception as effective as Telerig's.

In Byzantine tactics, the shock effect was achieved through a controlled charge of the cataphract heavy cavalry. At the Battle of Anchialus (763), this shock doctrine worked perfectly; an asymmetric infantry-cavalry coordination collapsed the Bulgarian center. The Bulgarians, on the other hand, achieved shock effect through ambush tactics. At the Rishki Pass, the sudden attack of light cavalry and archers in a narrow valley created a rout in the Byzantine ranks. Both sides applied shock effect in their own distinctive forms; however, the planned Byzantine shock tactic on the plains ultimately prevailed in strategic outcomes over the Bulgarian ambush shock in the passes.

Massed charges by Byzantine heavy cavalry had the potential to break Bulgarian lines on flat terrain. However, this effect was limited in mountainous areas. The Bulgarian horse archer tactics, conversely, disrupted Byzantine formations through continuous harassing fire and created shock.

The Balkan Mountains (Haemus) were the primary 'Earth' element determining the fate of these campaigns. The passes were a natural ally for the Bulgarians and an insurmountable barrier for the Byzantines. The Bulgarians leveraged this 'fatal terrain' at the Rishki Pass. 'Heaven' played a crucial role in the destruction of the Byzantine fleet twice. The great storm of 765, destroying 2,600 ships, clearly made nature an ally of Bulgaria. Amphibious landings at Black Sea ports depended on favorable seasons and winds. Throughout these campaigns, 'Heaven' (weather and sea state) and 'Earth' (mountains and passes) were the greatest variables in the face of human will.

The dense forests and narrow passes of the Balkan Mountains became deadly traps for the heavy Byzantine infantry. Bulgarian forces used this terrain to their advantage by employing ambush tactics. Furthermore, the Byzantine navy's heavy losses in two storms in the Black Sea demonstrated that weather conditions directly affected the war's outcome.

Intelligence asymmetry fluctuated dramatically during these campaigns. In the early campaigns, the Byzantines were almost blind to Bulgarian internal politics. Over time, both sides came to know one another. The breaking point was 774, when Telerig applied the maxim 'know yourself and know your enemy' precisely. Knowing the emperor's agents, he manipulated him with a trap letter. This significant asymmetric advantage gave the Bulgarians a respite. Overall, the party that did 'not know itself nor the enemy' was the Byzantines, because predicting the next leader and plan of an enemy governed by constant coups was impossible.

Constantine V had gained a significant advantage through agents placed inside Bulgaria before his campaigns. However, Telerig, via a fake asylum request, obtained and purged the list of Byzantine agents. Following this, Byzantium fell into intelligence blindness, while the Bulgarian side reversed the asymmetry thanks to its news sources within the Byzantine court.

Although the Byzantine strategy was based on attrition, Constantine V's ability to rapidly deploy the army and strike multiple points within the same campaign season was a successful application of the interior lines principle. The victory at Anchialus was made possible by the strategic maneuver capability provided by the navy. In contrast, the Bulgarians had a single advantage of interior lines — the Balkan passes. In these bottlenecks, they ambushed and defeated the larger Byzantine army piecemeal. Overall, strategic maneuver speed belonged to the Byzantines, while tactical speed belonged to the Bulgarians.

The Bulgarians used their interior line advantage to achieve rapid concentration in the Balkan passes. Byzantium, operating on exterior lines, had to conduct slow and predictable maneuvers. The speed of the Bulgarian cavalry often nullified Byzantine numerical superiority.

The morale multiplier was the most critical element of 'friction' determining the war's course. The Byzantine army was motivated by the rhetoric of 'soldiers of Christ' and a holy war ideology against the pagan Bulgarians. For the Bulgarians, the primary multiplier was the existential struggle of the tribes. However, constant struggles for the throne continuously eroded this high morale through constant 'friction'. The primary reason for the battlefield defeats of Telets and Vinekh was the collapse of their political support and the fragmentation of the army along tribal lines. Telerig's rise to power was a turning point for Bulgarian morale; he gathered the dispersed forces under a single will for the first time in a long while.

The Byzantine army faced opposition from some religious groups due to Constantine V's iconoclastic policies, negatively impacting morale. The Bulgarians, with their determination to preserve independence and warrior traditions, maintained high morale. However, internal political crises and changes of khans occasionally damaged the spirit of unity.

The Byzantine strategy indirectly attempted to apply the principle of 'winning without fighting'. Constantine V tried to sow discord among the Bulgarian nobility to fuel political instability in Pliska, but failed. The true 'victory without fighting' was achieved by Khan Telerig, who, in 774, neutralized the emperor without physical combat by deciphering the Byzantine agent network through a fake defection letter. This event is a classic example of Sun Tzu's dictum of subduing the enemy without fighting.

Byzantium initially attempted to wear down the enemy without fighting by exploiting Bulgaria's political crisis and internal dissensions. However, Telerig's masterful maneuver dismantled the Byzantine spy network and enabled Bulgaria to eliminate internal threats. This increased the Bulgarians' ability to resist without direct combat.