Rebellion
821–823 rebellion
The Rebellion of Thomas the Slav c. 820–823 was a large-scale Byzantine civil war, between the rebel forces of Thomas the Slav and the loyalist forces of Emperor Michael II. It spanned most Asia Minor and the Balkans, as Thomas layed siege to Constantinople, before he was ultimately defeated by loyalist forces, with the backing of the Bulgars.
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Text from the Wikipedia article “Rebellion of Thomas the Slav”, available under CC BY-SA 4.0.
The Rebellion of Thomas the Slav c. 820–823 was a large-scale Byzantine civil war, between the rebel forces of Thomas the Slav and the loyalist forces of Emperor Michael II. It spanned most Asia Minor and the Balkans, as Thomas layed siege to Constantinople, before he was ultimately defeated by loyalist forces, with the backing of the Bulgars.
Following the unsuccessful rebellion of Bardanes Tourkos against Emperor Nikephoros I in 803, Thomas fled within the Abbasid Caliphate. However, after Leo V ascended the throne, and following the abdication of Michael I Rangabe, Thomas was recalled was given command of the tourma of the foederati—a vital military division stationed within the strategically crucial Anatolikon Theme. On Christmas 820, Leo V was assassinated by the supporters of Michael II in the palace chapel. This action caused dissent across the empire, sparking revolts from the strategos of Sicily, Gregory (who was ousted and killed by Euphemius), and Thomas, who was proclaimed as emperor by the Anatolian Themes, with his base in the city of Amorium.
Beginning of the Rebellion
When the soldiers of the Anatolikon Theme and their commanders were informed of Leo's deposition by Michael they refused to acknowledge the new ruler, and instead chose a popular figure among their own ranks for the throne. They chose Thomas, a possible descendant of Slavic populations settled in Anatolia over the centuries, and an old veteran who had been a strong ally and close confidant of Leo amongst his officer cadre. As tourmarch of the foederati, Thomas portrayed himself as the champion of the common people of Anatolia, who had recently suffered from overtaxation under overbearing imperial policies, and of the army, which attracted the support he needed to quickly prepare and launch his rebellion within days to a few weeks following Leo’s assassination. Thomas' cause also took a religious dimension, as the he presented himself as an icondule restorationist against the imperial iconoclastic policies, receiving widespread support amongst both the military and civil-administrative officials in Asia Minor. Almost all of the Anatolian Themes, with the exceptions of the Opsikion and the Armeniakon, joined his rebellion. Ultimately, Thomas secured the loyalty of more than two-thirds of the empire's soldiers in Asia Minor during the opening stages of the civil war.
"The servant raised his hand against his master, the soldier against his officer, the rank-and-file soldier against his general"
— Vasiliev 1935, p.24
Despite the rapid progress of Thomas' rebellion, Michael maintained his powerbase in Constantinople, control over the central bureaucracy, and access to the treasury. He also took steps towards legitimising his rule by installing a new Patriarch of Constantinople, Antony I, who authenticated his sovereignty. Militarily, Michael enjoyed the support of the elite tagmatic units, in addition to all of the themes in Europe, as well as the Opsikion and Armeniakon in Asia Minor, along with the ducate of Chaldia. However, although the Armeniakon and Chaldia were accessible by sea, these territories were otherwise separated from Michael's seat of power. Michael considered possession of these northeastern territories strategically vital in countering Thomas' renegades, as he could threaten fromm there Thomas' Anatolikon heartland. He leveraged this by ordering the strategos of the Armeniakon, Olbianos, to march against Thomas with his troops. However, Thomas soundly defeated Olbianos' army in battle, a victory which he exploited with a successful counterinvasion of Michael's northeastern holdings, placing Chaldia and parts of the Armeniakon under his authority. However, before he could capture the entire theme, he was forced to divert his attention southwards to counter raids upon his lands by the Abbasids.
In spring 821, Michael's forces were temporarily reprieved due to the preoccupation of the latter with the Abbasids, who had launched raids into the rebel powerbase of the Anatolikon. However, rather than maintain a defensive response Thomas launched a counter-invasion into Abbasid Armenia. The province was especially vulnerable at the time, as the Abbasid governor and his army had sustained a heavy defeat by the Babak Khorramdin Khurramite rebels in the South Caucasus only months earlier. Thomas consequently invaded Armenia, defeated the depleted Abbasid armies that opposed him and completed his victory with a successful siege of Theodosiopolis.
Preoccupied with the threat of the Khurramite rebels, Caliph Al-Ma'mun sought to avoid further direct conflict with the Byzantines. Instead, his approach was exploit the Byzantines' own political turmoil, in order to neutralize the potential threat posed by them. For his part, Thomas also intended to refocus his military efforts toward the struggle against Michael, and consequently dispatched an embassy to Baghdad. The consequence was an alliance between the usurper and the Abbasids. Strategically, it was vital for Thomas to reach a settlement with the caliphate, as he would need to strip his Anatolian holdings of soldiers in order to initiate a decisive campaign into Europe and seize Constantinople. Thomas may have even sought to enlist Abbasid military support from the beginning of his revolt, though the raids by the latter had necessitated the military operations he conducted in Armenia. Thomas was said to have agreed to pay a small tribute to Baghdad, and in exchange al-Mam'un recognized his claim to the Byzantine throne and offered indirect support to his cause, allowing Thomas a state-sanctioned journey to Antioch, where he was crowned as emperor by the patriarch there. Thomas was also permitted to recruit volunteers, mainly Christians from the Abbasid territories along the Al-Thughur frontier, to bolster his forces. Consequently, he was unlike before able to renew his campaigns against Michael from a position of greater strength.
After consolidating his position in the east, Thomas assembled his troops and built his own fleet from the Cibyrrhaeot and Aegean Sea Themes to counter the imperial fleet stationed in the capital. Around this time, Thomas also adopted a young man named Constantius, to serve as his co-emperor and thereby entrench his political position with the establishment. Thomas then recalled the nephew of Leo, Gregory Pterotos, who had been exiled by Michael to the island of Skyros, and bestowed upon him command of the rebel naval forces. Thomas himself set off with his Thracesian army towards Abydos, having previously dispatched Constantius with an army ahead to complete the capitulation of the Armeniakon Theme. However, Constantius was ambushed and killed by the imperial loyalist troops under Olbianos, who followed his victory by dispatching a messenger bearing Constantius' severed head to Thomas' encampment at Abydos, a stratagem meant to demoralize the rebel faction.
Following this setback, Thomas replaced Constantius by adopting a former monk named Anastasius, granted him the title of co-emperor, and ordered the military preparations to continue without delay. Thomas ferried his massive army across the Hellespont and in the late October or early November of 821 and made landfall in Thrace, where the local inhabitants and garrison soldiers begun defecting to his army. Michael had recently marched into Thrace ahead of time with a small loyalist contingent to reinforce the regional fortresses and secure the people's loyalty, but after the locals deserted to Thomas en masse, Michael realized he was outnumbered and withdrew his remaining troops to safety behind the walls of Constantinople. Thomas arrived outside the city capital with roughly 80,000 men and set up his primary military camp at the Monastery of Saints Cosmas and Damian, located in the suburb of Blachernae (outside the northern land walls of Constantinople), as he assumed the city to quickly surrender, but the inhabitants refused and the city was besieged. Thomas first led his main force against the Theodosian Walls using siege engines, ordering a massive artillery barrage using catapults and mechanical siege towers. However, a brutal winter storm with freezing rain and severe wind gusts paralyzed the wooden machinery, snapping the ropes of his catapults and making ladders too slick to climb. In the spring, Thomas launched a massive coordinated naval attack under Gregory Pterotos against seaward walls along the Golden Horn. Michael II deployed his imperial dromon warships, unleashing Greek fire against the rebel fleet, incinerating the rebel ships, breaking Thomas' naval blockade, while killing many of Gregory Pterotos' sailors.
According to the historians Genesios and Theophanes Continuatus, while Thomas besieged Constantinople, Kanasubigi Omurtag had dispatched an embassy offering to intervene on behalf of Michael II against the usurper, which the emperor supposedly refused on the grounds that employing pagans to slay Christians was unthinkable. However, Omurtag invaded Thrace of his own accord, likely in November 822, and advanced towards Constantinople, which in turn prompted Thomas to detach his soldiers from the siege and march against the Bulgars. The two sides met at Kedouktos, near Heraclea, and according to Genesios the Bulgarians defeated Thomas, with Omurtag returning to Bulgaria with significant quantities of plunder. However, the account of the near-contemporary George Hamartolos claims the Bulgarian incursion had been brought about by the diplomatic machinations of Michael, who dispatched pleas to Omurtag for aid against Thomas, which forced Thomas to lift the siege in order to confront the Bulgars. According to George, Thomas defeated the Bulgars in battle, killing large numbers of their warriors, and forcing them out of Thrace. However, the victory may have been pyrrhic, with heavy losses on Thomas' own side, as the usurper was unable to resume the siege of Constantinople, and instead retired his army to his operating base at Arcadiopolis for the winter. Due to the propagandistic narrative of Genesios' account, most modern scholars consider George's account to be more reliable.
Although the confrontation with the Bulgarians had likely ended in victory for Thomas, it brought little strategic benefit for the rebel cause. The Bulgarian intervention had forced him to raise his siege of Constantinople, and the failure of this endeavour deteriorated the morale of the rebel army. Over the winter, contingents of the rebel forces began to desert or defect to Michael's side, and this in turn handed the strategic initiative to the loyalists. Michael II personally took the field, around spring 823, and confronted the exhausted rebel army under Thomas. The rebel force broke and fled, while some surrendered to Michael. After which, Michael had the remaining rebels besieged inside the fortified Arcadiopolis. After a grueling, starving months-long blockade, Thomas' own troops surrendered him to the emperor in exchange for a pardon. Thomas was brought before the emperor outside of the city, fell to the ground and begged for mercy, prostrating himself and weeping at his rival's feet where he is claimed to have pleaded:
Have mercy on me, oh True Emperor
According to some accounts, Michael hesitated and showed a brief moment of pity, until the emperor's chief adviser, John Hexaboulios, urged him to be ruthless, warning that sparing a charismatic rebel would only invite future civil wars. Thomas was then dismembered and impaled on a stake alongside his adopted son, Anastasius, thus ending the three-year long rebellion.
Text from the Wikipedia article “Rebellion of Thomas the Slav”, available under CC BY-SA 4.0.