Draft:Rebellion of Thomas the slav

The Rebellion of Thomas the Slav c. 820–823 was the largest yet most destructive civil wars in the history of the Byzantine Empire, spanning throughout most Asia Minor and the Balkans, which saw the rebel army even lay siege to Constantinople itself before ultimately being defeated by Emperor Michael II with the backing of the Bulgars.

Rebellion of Thomas the slav
Part of The Byzantine civil wars Arab–Byzantine wars Byzantine-Bulgarian wars
Depiction of Thomas on horseback and dressed as a Byzantine emperor, negotiating with the Arabs. from the (Madrid Skylitzes) version of the chronicle of (John Skylitzes).
Date December 820–October 823 Location Asia Minor • Balkans Result Victory for Michael II
Belligerents
Forces of Michael II First Bulgarian Empire	Forces of Thomas Abbasid Caliphate Principality of Iberia
Commanders and leaders
Michael II Gregory Pterotos † Olbianos Katakylas Khan Omurtag	Thomas the Slav  Gregory Pterotos   Philip † Anastasius Al-Ma'mun Ashot I of Iberia
Strength
c. 35,000	c. 80,000

Background

Following the unsuccessful rebellion of Bardanes Tourkos against Emperor Nikephoros I in 803, Thomas would fall into obscurity where he fled within the Abbasid Caliphate however after Leo V the Armenian ascended the throne after the abdication of Michael I Rangabe he was recalled and handed him the command of the Foederati—a vital military division stationed within the strategically crucial Anatolikon Theme. However on Christmas day in 820, Emperor Leo V the Armenian was assassinated by the supporters of Michael the Amorian in the palace chapel. This action caused dessent across the Empire, with the strategos Gregory of Sicily retaining allegience to Leo and defying Michaels authority. However, Gregory was soon ousted and killed by the faction favourable to Michael in Sicily, led by Tourmarches Euphemius. This event proved significant in the following civil war, as it allowed maritime elements from Sicily to sail East and reinforce Michael's navy. Michael would soon face a far more dangerous opponent from the East, where Emperor Leo had built up a loyal base of support during his reign. The anatolics, upon learning of the news of Leo's demise, proclaimed a rival claimant Thomas, who was based in Amorium, as Emperor.

Rebellion

Beginning of the Rebellion

Thomas defeats a loyalist imperial force on behalf of Michael

When the soldiers of the Anatolikon theme and their commanders were informed of Leo's deposition by Michael there was outrage. These men refused to acknowledge the new ruler, and instead chose a popular figure among their own ranks to challenge the throne. This man was Thomas 'the Slav', a possible descendant of Slavic populations settled in Anatolia over the centuries and an old veteran soldier who had been a strong ally and a close confidant of Leo among his officer cadre. As Tourmarch of the Federates Thomas portrayed himself as the champion of the common men of Anatolia, who had recently suffered from overtaxation under overbearing Imperial policies or corrupt governors, and of the soldiery, while also styling himself as the avenger of Leo, which attracted all 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 Slav was able to present himself as an icondule restorationist against the iconoclastic policies of Leo V and his successor Michael (despite the efforts of Michael II to reconcile with Icondules and end persecutions against them), attracting many adherents of this Thomas received widespread support among both the military and civil-administrative officials (such as Tax collectors) in Asia Minor, and almost all of the themes except the Opsikion and the Armeniac joined him. The civil war thus emerged out of rival bids for power by Michael and Thomas over Leo V's succession. Ultimately, Thomas secured the loyalty of more than two-thirds of the empire's soldiers in Asia Minor during the opening stages of his revolt.

"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

Themes of Asia minor during the reign of Michael III c. 864, late in the Amorian era

Despite the rapid progress of Thomas' revolt, Michael maintained his powerbase in Constantinople and along with it control over the central bureaucracy and access to the treasury, and took steps toward legitimising his rule by having the patriarch of Constantinople authenticate 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 aforementioned Opsikion and Armeniac territories in Asia Minor, along with the ducate of Chaldia. Although Armeniakon and Chaldia were accessible by sea, these territories were otherwise seperated from Michael's seat of power by Thomas' territories. Michael considered possession of these Northeastern territories strategically vital in countering Thomas' renegades as he could threaten Thomas' Anatoliokon heartland from there, and he immediately leveraged this by ordering Armeniac strategos to march against Thomas with his troops. However, Thomas soundly defeated Olbianos' Armeniacs in battle, a victory which he exploited with a counterinvasion of Michael's Northeastern holdings. This expedition was successful, and Thomas was able to place Chaldia and parts of the Armeniac territories under his authority. However, before he could capture the entire Armeniac theme from Olbianos, Thomas' was forced to divert his attention Southwards to counter raids upon his lands by the Abbasids.

Conflict and Alliance with the Abbasids

Golden dinar of caliph al-Ma'mun

In spring 821, Michael's forces were temporarily reprieved from the onslaught of Thomas due to the preoccupation of the latter with the Abbasids, who had launched raids into his powerbase in the Anatolikon. However, rather than maintain a defensive response Thomas intended to trade blows with the Arabs by launching a counter-invasion into Abbasid Armenia. This province was especially vulnerable at this time, as the Abbasid governor and his army had sustained a heavy defeat in his attempt to suppress the uprising of Babak Khorramdin's Khurramites in Azerbaijan only months earlier. Thomas consequently invaded Armenia and crushed the depleted Abbasid armies which attempted to oppose him, and he completed his victory with a successful siege of Theodosiopolis.

Preoccupied with the threat of the Khurramite rebels, Caliph Al-Ma'mun sought to avoid a direct conflict with the Byzantines. Instead, his approach was exploit the Byzantines' own political turmoil 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 against Michael and seize Constantinople. In fact, Thomas may have sought to enlist Abbasid military support from the beginning of his revolt, though the raids by the latter had necessitated the military operations Thomas conducted in Armenia. Thomas was said to have agreed to pay a minor 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 Orthodox patriarch there. Thomas was also permitted to recruit volunteers, mainly Christians from the Abbasid territories along the Thughur frontier, to bolster his forces. Consequently, Thomas was able to renew his campaigns against Michael from a position of even greater strength than before.

Assault on Constantinople

• Crossing and siege of Constantinople

Assault on constantinople

After consolidating his position in the East, Thomas assembled his troops and built his own fleet from the Cibyrrhaeot and Aegean Sea naval themes to counter the imperial fleet stationed in the capital. Around this time, Thomas also adopted a young man whom he named Constantius, to serve as his co-emperor and thereby entrench his political position with the establishment of a clear line of succession. The origins of this Constantius are not well known. Thomas then recalled the nephew of Leo named 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 toward Abydos, having previously dispatched Constantius with an army ahead to complete the capitulation of the Armeniac theme to his faction. 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 and 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 late October or early November of 821, thomas made landfall in thrace where the local inhabitants and garrison soldiers of Thrace greeted him with immense fervor and defected 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 loyal troops to safety behind the walls of Constantinople, Thomas then 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 surrender out of sheer terror, but the inhabitants refused and the city was besieged. Thomas first led his main force against the Theodosian Walls using siege engines and ordered a massive artillery barrage using catapults and mechanical siege towers. However, a brutal winter storm with freezing rain and severe wind gusts paralyzed his wooden machinery, snapping the ropes of his catapults and making ladders too slick to climb, In the spring, Thomas then Orchestrated a massive coordinated naval attack under Gregory Pterotos to breach the seaward walls along the Golden Horn, Michael II deployed his imperial dromon warships, unleashing Greek Fire against the rebel fleet. The incendiary weapon utterly incinerated the rebel wooden ships, breaking Thomas's naval blockade and causing massive casualties among Gregory Pterotos's sailors.

Bulgarian intervention and Battle of Kedouktos

The Bulgarians under Omurtag attack Thomas' army at Kedouktos

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 Bulgarians. The two sides met at the Kedouktos near Heraclea, and the outcome where Genesios claims the Bulgarians defeated Thomas, with Omurtag returning to Bulgaria with significant quantities of plunder. However, the version of events recorded in the near-contemporary The near contemporary account of George the Monk is different. According to George the Bulgarian incursion had been brought about by the diplomatic machinations of Michael, who dispatched pleas to Kanasubigi for aid against Thomas, which forced Thomas to lift the siege to confront the enemy. According to George, Thomas defeated the Bulgarians in battle, killing huge numbers of the Kanasubigi's 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 more reliable.

Climax

surrender and humiliation of Thomas

Although the confrontation with the Bulgarians had likely ended in victory for Thomas, this victory brought little strategic benefit for the usurper's cause. In any case, the Bulgarian intervention had forced Thomas to raise his siege of Constantinople and the failure of this endeavour deteriorated the morale of Thomas' men. Over the winter, contingents of the usurpers army began to desert or defect to Michael's side, and this in turn handed the strategic initiative to the Emperor's side. Following his departure from Constantinople, a smaller faction of Thomas' men sought refuge in the nearby city of Panion, Michael II personally took the field and trapped Thomas and his remaining loyalists inside the fortified town of Arcadiopolis. After a grueling, starving months-long blockade, Thomas' own troops surrendered him to the Emperor in exchange for a pardon.

Aftermath

Saracens sail against Crete

After the devastating three-year civil war had ended with the execution of thomas in 823, the aftermath resulted in long-term consequences which dramatically weakened the Byzantine Empire and its naval fleet alongside exhausting the empire’s treasury weakening the economy and military which left the frontier in Asia Minor and the empire completely vulnerable to foreign invasion, where external powers soon exploited. The following year (824) Andalusian exiles successfully captured Crete establishing the Emirate of Crete, during the civil war, thomas had pulled all of the elite garrison troops from the Byzantine-Arab frontier to march on Constantinople, where the frontier was left exposed to potential Abbasid invasions, Al-Ma'mun immediately sought out to conduct annual summer raids (ṣā'ifa) the following year as a test to the remaining strength of the defenses. However, Abbasid forces sustained defeats at the hands of Byzantine forces during their raiding expedition in 825. Two years later, the Aghlabids in the west began their Conquest of Sicily followed by the rebellion of Euphemius.

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