1. Historical context

The protagonists of the rebellion of Thomas, described as ‘the Slav’ in recent scholarship due to his origins,¹ are closely connected with him since July of 803. The strategos of the theme of Anatolikon, Bardanes the so-called ‘Turk’, had rebelled against Emperor Nikephoros I with the cooperation of a group of devoted military men: Leo the Armenian (Leo V), Michael of Amorion and Thomas.² Contrary to the first two, who finally joined forces with Nikephoros and received high offices, Thomas remained faithful to Bardanes, which resulted in his disappearance from the political fore following the failure of the rebellion.³ He reappeared when his former companion Leo the Armenian ascended on the imperial throne, honouring him with the office of tourmarch of the Foederati, a position Thomas maintained throughout Leo’s reign, residing at the base of his unit, in the theme of Anatolikon. In the early hours of Christmas day of 820, Leo V was murdered, after a conspiracy of followers of Michael of Amorion, and the latter acceded to the throne as Michael II. In order to avenge the murder of his friend and emperor, and punish the culprit, with whom he always had personal differences, but also to pursue his own political ambitions, Thomas refused to recognize the new emperor and immediately rebelled against him, accusing Michael as a usurper and promoting himself as a guardian of imperial legitimacy.⁴

The circumstances during the outbreak of the rebellion were favourable. Although the office Thomas held was not the highest-ranking in the hierarchy of the theme of Anatolikon, the fact that his military base was in the theme’s seat, the city of Amorion, afforded him significant power. Furthermore, his long military career, already since Bardanes’ time, and Thomas’ military and intellectual talents had made him especially popular among the soldiers of Asia Minor. Thomas’ popularity becomes even more important if we consider that during the same period Michael II, a man largely obscure up to then and disagreeable due to his reported vices and of dubious martial prowess, had not had enough time to become established in the minds of his subjects as emperor and founder of a new dynasty. Under these circumstances, Thomas’ rebellion did not really threat an established imperial legitimacy, as in the case of similar rebellions in the history of the Byzantine Empire. The fact, however, that it broke out immediately after Michael II’s coronation at Constantinople made it appear more of a clash between two equal military officials over the throne. Thomas’ strong and familiar to the citizens of Asia Minor personality, coupled with the fact that he had no part in the murder of Leo V who also enjoyed wide support in the area, worked to his advantage. The social and economic conditions that prevailed in Asia Minor during that time also influenced positively the way the people viewed the outbreak of the rebellion.⁵ More specifically, there was intense discontent among the farmers because of the onerous taxation imposed by the distant capital, but also because of the aberrations of the state officials against them. This atmosphere favoured the direct support of a rebellion that turned against the central administration, especially one that was led by a familiar and popular official.⁶

2. The rebellion of Thomas

2.1. Outbreak of the rebellion in Asia Minor

Immediately after December 25, 820 the tourmarch of the Foederati Thomas the Slav rebelled against Michael II and was proclaimed emperor by the troops of the theme of Anatolikon. Within a short period he had won the support of most of the thematic troops of Asia Minor, as well as that of the Kibyrrhaioton fleet.⁷ He was also joined by state officials, among which were local tax collectors, who offered him the income resulting from the taxes in their areas. Only Katakylas and Olbianos remained faithful to Michael II - they were the strategoi of the themes of Opsikion and of Armeniakon respectively.⁸ Apart from the support of the thematic army, Thomas aimed at securing military help from the populations residing northeast of the imperial borders (Iberians, Armenians and Abkhazians).⁹ Michael II, who followed the developments in Asia Minor from Constantinople, ordered the troops loyal to him to move against Thomas.¹⁰ In the battle that followed the forces of Michael II were turned to flight, while Thomas penetrated as far as Chaldia, which he placed under his control. Taking advantage of this internecine conflict, the Arabs intensified their land and sea raids against Asia Minor, which forced Thomas to temporarily postpone his offensive, as he had to deal dynamically with the danger facing the areas that supported him and could not successfully wage war on two fronts at the same time. Thus, probably in the spring of 821, Thomas led a campaign against the Arab lands,¹¹ at the same time dispatching an embassy to the Arab caliph al-Mamūn (813-833).

The negotiations that ensued finally led to the creation of an alliance between Thomas and the Arabs against Michael II.¹² Thomas then travelled to Antioch of Syria, where the Orthodox Patriarch Job crowned him emperor, with the consent of al-Mamun. Thomas also adopted a young man, to whom he gave the name Konstantios, so as to have an heir. Controlling the largest part of the coasts of Asia Minor, Thomas built a fleet of warships and transports to reinforce the thematic fleet that awaited his orders at Lesbos. Leading his land army he moved towards Abydos, aiming to join forces with his fleet and transport his troops to Thrace, in order to assail Constantinople, as only the capture of the capital could legitimize his ascend to the throne, both on a real and a symbolic level. While Thomas was in Abydus, Konstantios joined battle with Olbianos, was defeated and killed. Michael II, who still enjoyed the support of the tagmata and of the imperial fleet, was keen to retain the favour of the themes that had not sided with Thomas at the outset, i.e. the themes of Armeniaca and Opsikion. Thus as a reward for their loyalty he cut the sum their subjects had to pay for the kapnikon tax for that particular year by half. When Thomas’ activities on the northern coasts of Asia Minor revealed that he was planning to attack Constantinople through Thrace, Michael II attempted to secure the allegiance of the Thracian cities and strengthened their defences with fortification works so that they could withstand Thomas’ offensive. He also recalled the strategoi Olbianos and Katakylas with troops from their themes, reinforced the walls of Constantinople and barred entrance to the Golden Horn inlet by pulling a huge chain across it.

2.2. Abortive siege of Constantinople

Thomas sailed from Abydus to Thrace in October or November of 821. The inhabitants greeted him with enthusiasm and many willingly enlisted in his army.¹³ A combined assault was to be launched on Constantinople by land and sea simultaneously. Thomas appointed Gregorios Pterotos¹⁴ as commander of the land forces, while the entire rebel fleet sailed from Abydus to Constantinople. Meeting no resistance from the imperial warships, the fleet broke through the chain and entered the Golden Horn inlet, up to the estuary of the Barbyses River, awaiting Thomas’ arrival. Thomas marched off to Constantinople leading the rest of his land forces, accompanied by a former monk named Anastasios, whom he adopted in place of the deceased Konstantios. Thomas’ hopes that the inhabitants of the capital would cower seeing the size of his forces and immediately surrender the city were disproved. Thus he was forced to make camp north of the city, near the monastery of Ss Cosmas and Damian. From there he dispatched troops to capture the coasts from Thrace to the Pontus and, in December of 821, he launched a naval and land offensive against Constantinople. The weather conditions, however, hampered his military operations and thus he decided to temporarily postpone them. Michael II took advantage of this and reinforced Constantinople’s defences with forces troops the themes of Armeniakon and of Opsikion. In the spring of 822 Thomas resumed his offensive on Constantinople with greater intensity, failing however to achieve the desired results. Thus, many of his soldiers begun defecting to Michael II, who had promised amnesty to them. Gregorios Pterotos accompanied by a small military force also tried to defect to the enemy camp. Thomas, however, realized this soon enough, arrested Gregorios and put him to death. On the occasion of this success Thomas declared that he had beaten Michael II’s forces on both land and sea and requested that the theme of Greece, the Peloponnese and the Aegean islands provide him with more warships so as to capture Constantinople. Indeed, in the summer of 822 new ships arrived and harboured in the port of Byridoi, north of the Propontis.¹⁵ Yet, before this fleet had a chance to join with the rest of the rebel forces it came under attack by the imperial fleet, resulting in most of the ships being destroyed by Greek fire, or captured by the enemy – only a small portion managed to safely reach their destination. Notwithstanding this success, Michael II still did not possess enough troops to launch an attack and finally lift the siege of Constantinople. Thus, calling upon a treaty signed during the reign of Leo V, he asked the Bulgariankhan Omurtag to attack Thomas.¹⁶ In November of 822 the Bulgarians invaded the Byzantine lands, forcing Thomas to move against them with his entire army. In the battle that was joined in the plain of Kedouktos, situated between Heraclea and Selymbria, both armies suffered heavy casualties. The Bulgarians retreated to their lands, but Thomas was unable to return to Constantinople to continue his siege for wintertime was advancing and he no longer possessed a fleet: his last ships had surrendered to Michael II while he was fighting the Bulgarians. Thus he set up camp in the plain of Diabasis, approximately 40km west of the capital.¹⁷

2.3. Suppression of the rebellion

When in the spring of 823 Thomas resumed his offensive making raids into Thrace, Michael II decided to campaign against him, accompanied by forces from the themes of Armeniakon and of Opsikion. In the battle that was fought in the plain of Diabasis (April or early May of 823) Thomas’ troops, weary of the three-year war, took to flight. Many surrendered to Michael II; others, under Anastasios, Thomas’ adopted son, sought refuge at Bizye and in other fortresses of Thrace, while a part of the army under Thomas sought refuge in Arcadiopolis.¹⁸ Michael II pursued Thomas and laid siege to Arcadiopolis for five months, a period during which the people managing to escape the siege sought refuge at Bizye. Finally, in mid-October of 823 the exhausted by the famine inhabitants of Arcadiopolis conspired against Thomas and handed him to the emperor, who had him mutilated and then killed. When this happened, the inhabitants of Bizye handed in Anastasios, who met a similar fate. Although the rebellion of Thomas had been decisively crushed, some of his followers in Thrace, taking cover in Panion and Heraclea, continued to oppose Michael II.

An earthquake that occurred in February of 824 destroyed the walls of Panion forcing those inside it to surrender, while the damage caused to the walls of Heraclea facilitated its capture soon after by the imperial forces. Early in March of 824 Michael II returned to Constantinople victorious, where he made a triumph, parading the chained followers of Thomas in the Hippodrome. Still, two of Thomas’ officials in Asia Minor, Choireus and Gazarenos Koloneiates, refused the high offices offered to them by Michael II to recognize him as emperor and continued to launch raids, the former using Kaballa (northwest of Ikonion) as his staging grounds, the latter using Saniana (southeast of Ankara). Michael II finally convinced the inhabitants of these two fortresses to not readmit Choireus, Gazarenos Koloneiates and their troops upon their return from yet another raid. To save themselves, they were forced to move towards the territory of the Arabs, but they were intercepted by the forces of Michel II and were put to death.

3. Consequences

The rebellion of Thomas the Slav, which is the most important event in the internal political scene during the reign of Michael II, weakened the Byzantine Empire at all levels. It developed into a fully-fledged civil war which lasted three whole years, specifically because the two sides were more or less evenly matched in terms of their military forces and thus could not strike a decisive blow to their opponent. The fleet of the empire (thematic as well as imperial) suffered the greater losses. Notwithstanding the fact that the casualties among the land forces were not so great, the thematic army was also weakened by the protracted warfare. All these negatively impacted the defensive abilities of the Byzantine Empire which would soon be unable to stop the capture of Crete by the Arabs of Spain, as well as the African Arabs’ invasion in the Byzantine lands of Sicily in 827. These failures in the area of the Mediterranean forced Michael II and his successor Theophilosto focus their attention on the defence of Asia Minor against the attacks of the Eastern Arabs. The consequences on the financial and social level were also grave. The extensive destruction reeked upon various areas of the empire, and mainly Thrace, due to the prolonged presence of large military contingents, the armed clashes and the raids threw their economic life into disarray. The religious policy Michael II followed was largely formulated in the aftermath of Thomas’ rebellion, for the adoption of Iconoclasmby himwould prove that he was a true heir to Leo V, who also opposed the veneration of the icons.¹⁹ With respect to foreign diplomacy, Thomas’ rebellion firmly established an alliance between the Byzantines and the Bulgarians that continued in the following decades. Finally, apart from the exemplary punishment of the rebel and his adopted son, as well as the execution of some of his followers, Thomas’ rebellion did not have grave consequences on individual persons, as the victorious Emperor Michael II was rather merciful towards his vanquished foes, sentencing to exile only those he deemed most dangerous.