The Byzantine–Hungarian War between 1162 and 1167 were a series of frontier campaigns and dynastic proxy conflicts fought between Byzantine Empire and the Kingdom of Hungary, which was primarily fought within the strategic regions of Dalmatia, Croatia, and Sirmium along the Danube and Sava river valleys. Instigated by Manuel I Komnenos, the war served as a direct intervention in the Hungarian succession crisis following the death of King Géza II. The war geopolitically constituted a struggle for hegemony over critical river corridors and maritime trading ports that controlled access to the wider Balkan peninsula which eventually reached its decisive climax at the Battle of Sirmium.
Background With the conclusion of the previous Byzantine–Hungarian war settled, King Géza II would consider on a five-year truce with the Byzantine Empire in 1155 which was extended in 1161 for another five years by 1161. However, Géza’s death in the ensuing year of 1162 would consequently create a succession crisis between his fifteen year old son, Stephen III and his exiled brothers Ladislaus and Stephen IV. Who both became rival claimants to the Hungarian throne During Géza’s reign, Stephen IV had previously attempted an unsuccessful opposition against his brother, forced into exile, the prince sought refuge at Regensburg within the Holy Roman Empire, appealing to the emperor, Frederick I Barbarossa, the emperor would host an imperial council (or "diet") to address the situation before ultimately declining Stephen’s plead for assistance.In conclusion of Barbarossa’s denial, Stephen IV made way for Constantinople where he sought refuge at the imperial court, not long after, Ladislaus would also appear in the imperial court where they became important political figures under the protection of the Byzantine Emperor Manuel I Komnenos. While there, Stephen was greeted and arranged in marriage with the emperor’s niece, Maria Komnene.The presence of both claimants at the imperial court would provide Manuel an opportunity to directly intervene in the Hungarian succession crisis, where he initially favored Stephen and began preparing military aid on the behalf of Stephen IV’s return to Hungary, which also gave Manuel an avenue to strengthen Byzantine influence over the contested territories disputed between the two powers.
Byzantine–Hungarian war Byzantine intervention and the accession of Ladislaus II With Manuel’s support secured, the prince proceeded towards Hungary while accompanied with a Byzantine force under the command of Alexios Kontostephanos en route,while Manuel himself separately advanced with the imperial army toward the Hungarian frontier to reinforce the intervention, bringing substantial military pressure to bear upon the position of Stephen III. While at Haram, Manuel’s envoys entered into negotiations with the Hungarian magnates, seeking to secure their recognition of Stephen IV, however, opposition to his accession remained sufficiently strong that the magnates instead agreed to recognize his elder brother, Ladislaus as king, declaring him as Ladislaus II. The arrangement at Haram allowed the magnates to reject Stephen IV’s immediate accession while avoiding a direct confrontation with the Byzantine emperor and preserving the possibility of continued Byzantine support. Stephen III subsequently attempted to maintain his position against the new settlement, but his forces were defeated by the Byzantine army under Alexios Kontostephanos at Kapuvár.
The defeat forced Stephen III to abandon Hungary and seek refuge in Austria, where he remained for approximately six weeks before returning to contest the authority of Ladislaus II. King Ladislaus sought to consolidate his authority with continued Byzantine support appointing prince Stephen IV as the duke of both Croatia and Dalmatia and designating him as his successor, which allowed the Byzantine-backed faction to retain a prominent position within the Hungarian political order. Despite the initial political consolidation, Ladislaus II’s position remained precarious, as Stephen III persisted in opposing his authority and retaining support among sections of the Hungarian nobility. Ladislaus was unable to establish uncontested authority over the kingdom. Regardless of the circumstances, Ladislaus remained king under Byzantine protection until his unexpected death in early 1163, allowing Stephen IV to succeede Ladislaus as king. Who also attempted to secure the throne but quickly faced intense opposition from the nobility and the Archbishop Lucas of Esztergom who refused to crown him as both the Hungarian nobles and the Archbishop deemed Stephen IV as a tyrannical usurper and a submissive Byzantine puppet, getting excommunicated by Lucas.O City of Byzantium, Annals of Niketas Choniates (4.127), p. 72.
Return of the king and settlement between Byzantium–Hungary
Upon the return of Stephen III from exile, Stephen IV’s reign was again forced into exile following a renewed opposition from his nephew where he suffered a decisive defeat at Székesfehérvár against his namesake which effectively brought his attempts to secure the Hungarian throne to an end. Stephen IV was captured amidst the fighting, but was subsequently released by Stephen III, allowing him to Re-evaluate his luck in the Holy Roman Empire, appealing to Frederick Barbarossa once more, offering submission and geopolitical alignments if the German knights would march into Hungary and restore his crown, to no avail, prompting Stephen IV to again depart for Constantinople for further support from Manuel.
The emperor initially continued to consider restoring Stephen IV, however, the failure at Székesfehérvár demonstrated the difficulty of restoring Stephen IV to the Hungarian throne while Stephen III continued to command support among the Hungarian nobility. Thus, Manuel abandoned any further attempts to restore Stephen IV and instead pursued a negotiated settlement with Stephen III, which required the recognition of his authority in exchange for the transfer of Sirmium and other contested territories to Byzantine control relinquishing his assistance on behalf of Stephen IV, bringing the immediate succession dispute to an end.
With the agreements in place and the emperor’s abandonment to restore Stephen IV to the throne, Manuel turned his attention towards the younger brother of Stephen III and Stephen IV, in lieu of Stephen IV, Béla, whom Stephen III previously agreed to be escorted to the imperial court in Constantinople by George Palaiologos, the Sebastos by the end of 1163, without the exception of control of of Béla's possessions. Béla was betrothed to Manuel’s daughter Maria Komnene and granted the title of despot or (“lord”), renaming him to Alexius. Becoming known at the imperial court as "Béla-Alexios" likely attributing to the AIMA prophecy, Béla was subsequently arranged as Manuel’s heir.
Manuel sought to establish Béla’s inheritance over the contested territories, providing the emperor with a new dynastic basis for maintaining his influence in Hungarian affairs. In spite of Stephen III’s acceptance of the settlement, Manuel’s elevation of Béla ensured that the territorial question remained unresolved. When the dispute over Béla’s inheritance again brought Stephen III and Manuel into direct military confrontation.
Stephen III subsequently moved to reassert Hungarian control over the territories claimed for his younger brother, challenging the political and territorial arrangement that Manuel had attempted to impose through the preceding negotiations, prompt Manuel to abandon preparations for a campaign in Cilicia and turn his attention toward the Hungarian frontier.
In regard of Stephen’s reassertion over béla’s duchy, the emperor personally assembled a large army and advanced personally toward the Danube, accompanied by Béla and Stephen IV alongside the imperial army, presenting the expedition not as a war against the Hungarian kingdom itself, but as an attempt to recover Béla’s inheritance and enforce the arrangements previously made concerning his lands.
Amid the Byzantine advance, Stephen sought assistance from neighboring rulers and assembled his own forces rather than abandoning the disputed territories without resistance, gaining received support from Vladislaus II of Bohemia, while additional assistance came from Austria and Halych. The mobilization of the Hungarian forces, supported by foreign contingents, brought the two armies into close proximity without immediately producing a decisive engagement.
Rather than risk a costly battle, Manuel sought to compel Stephen III to accept the restoration of Béla-Alexios’s territories through negotiation, presenting his demands as the enforcement of agreements already reached between the two rulers. When the Hungarian king and his representatives were confronted with the emperor’s demands, Manuel personally addressed Stephen III and explained the purpose of his expedition:
The Hungarian representatives subsequently offered to "restore" the disputed territories, apparently seeking to avert a wider confrontation through the terms of the earlier settlement.
Manuel, however, initially rejected the proposal on the grounds that the territories in question had already fallen under Byzantine control during the campaign.
Nevertheless, Manuel ultimately accepted oaths guaranteeing the settlement, the agreement temporarily secured the territories claimed for Béla and demonstrated the increasing extent of Byzantine military and political influence in the western Balkans.
Hungarian counteroffensive of 1165–1166
The dispute intensified again in 1165, when Stephen III launched another campaign against Sirmium and besieged Stephen IV at Zimony. Stephen IV was killed during the siege, after which the fortress fell to Hungarian forces. His death removed the principal claimant whom Manuel had previously supported in his attempts to influence the Hungarian succession, but it did not lead the emperor to abandon his wider objectives. In lieu of Stephen IV the emperor preceded to pursue the territorial interests associated with Béla, while the possession of Sirmium remained central to the struggle between the two powers.
Manuel initially faced an internal challenge from his cousin Andronikos Komnenos, whose rebellion delayed the emperor’s immediate response, but after neutralizing the threat Manuel resumed the offensive. By late June, he personally advanced toward Zimony with a Byzantine army and recaptured the fortress, while other imperial forces operated in Bosnia and Dalmatia.
Byzantine control was further reinforced by military garrisons and administrative measures in the recovered territories, while Venetian naval intervention in Dalmatia assisted the Byzantine position and helped restore Venetian authority at Zadar. Faced with the renewed Byzantine advance, Stephen III was compelled to negotiate and renounce his claims to Sirmium and Dalmatia, however the settlement again failed to produce a lasting resolution.
In the spring of 1166, ispán Denis mustered an army and advanced toward Sirmium, where Byzantine forces stationed there were defeated, allowing the Hungarians to almost entirety reverse all of the prior Byzantine gains with the exception of Zimony.
Transylvanian campaign
Manuel responded by dispatching three separate Byzantine armies against the Hungarians. The first, commanded by Alexios Axouch accompanied by Béla, advanced toward the Danube and served to divert Hungarian attention, giving the illusion that the Byzantines would again be directed toward the western frontier. Meanwhile, Byzantine forces under Leo Batatzes and John Doukas advanced into Transylvania and eastern Hungary as part of a broad pincer movement.