Alexios I of Trebizond in the context of "Siege of Trebizond (1205–06)"

The Empire of Trebizond or the Trapezuntine Empire was one of the three successor rump states of the Byzantine Empire that existed during the 13th through to the 15th century. The empire consisted of the Pontus, or far northeastern corner of Anatolia, and portions of southern Crimea.

The Trapezuntine Empire was formed in 1204 with the help of Queen Tamar of Georgia after the Georgian expedition in Chaldia and Paphlagonia, which was commanded by Alexios Komnenos a few weeks before the Sack of Constantinople. Alexios later declared himself emperor and established himself in Trebizond (now Trabzon in Turkey).

The Trapezuntine emperors were the rulers of the Empire of Trebizond, one of the successor states of the Byzantine Empire founded after the Fourth Crusade in 1204, until its fall to the Ottoman Empire in 1461. All but two of the Trapezuntine rulers belonged to the Komnenos dynasty, which had previously ruled the Byzantine Empire from 1081 to 1185. They initially claimed to represent the legitimate line of Roman emperors, in opposition to the Latin Empire in Constantinople, the Laskaris dynasty of the Nicene Empire, and the Komnenos Doukas family of Epirus and Thessalonica. To emphasize their dynastic claim, Trapezuntine emperors from the late 13th century onwards styled themselves as Megas Komnenos (Μέγας Κομνηνός, lit. 'Grand Komnenos').

Out of the Byzantine claimants that emerged in 1204 and thereafter, the Trapezuntine emperors, despite their illustrious descent, had perhaps the worst position. Not only were they far away from Constantinople in a peripheral province of the empire, but the reputation of the Komnenoi had been severely damaged by the detested last emperor of the dynasty, Andronikos I Komnenos (r. 1183–1185), grandfather of the first Trapezuntine emperor Alexios I (r. 1204–1222). Though they continued to claim to be the legitimate rulers of the entire former Byzantine Empire for decades thereafter, conflict with the Nicene Empire and the Sultanate of Rum in the early 13th century reduced the power of the Trapezuntine emperors. After the fall of Sinope to Sultan Kaykaus I in 1214, the Empire of Trebizond ceased to be a major contender for restoring the Byzantine Empire and became reduced to a small and local power.

Theodore I Komnenos Laskaris or Lascaris (Greek: Θεόδωρος Κομνηνὸς Λάσκαρις, romanized: Theodōros Komnēnós Láskaris; c. 1175 – November 1221) was the first emperor of Nicaea—a successor state of the Byzantine Empire—from 1205 to his death. Although he was born to an obscure aristocratic family, his mother was related to the imperial Komnenos clan. He married Anna, a younger daughter of Emperor Alexios III Angelos in 1200. He received the title of despot before 1203, demonstrating his right to succeed his father-in-law on the throne.

The Fourth Crusade forced Alexios III to flee from Constantinople in 1203. Theodore was imprisoned by the crusaders (commonly referred to as "Latins" by the Byzantines), but he escaped. After crossing the Bosporus into Asia Minor (in present-day Turkey), he started to organise the local Greeks' resistance against the Latins in Bithynia in his father-in-law's name. He concluded an alliance with the Seljuq sultan of Rum, but he could not stop the Latins' expansion. Neither could he prevent a claimant to the imperial throne, Alexios Komnenos, from establishing a Byzantine successor state, the Empire of Trebizond, in northern Asia Minor. Theodore's position consolidated only after Tzar Kaloyan of Bulgaria inflicted a crushing defeat on the Latins in the Battle of Adrianople (in Thrace) in 1205.

David Komnenos (Greek: Δαβίδ Κομνηνός, Georgian: დავით კომნენოსი) (c. 1184 – 1212) was one of the founders of the Empire of Trebizond and its joint ruler together with his brother Alexios until his death. At least two lead seals and an inscription found on a tower in Heraclea Pontica attest that he was the first of his family to use the style Megas Komnenos. Ηe was the son of Manuel Komnenos and grandson of the Emperor Andronikos I.

The siege of Sinope in 1214 was a successful siege and capture of the city by the Sultanate of Rum under their Sultan, Kaykaus I (r. 1211–1220). Sinope was an important port on the Black Sea coast of Anatolia, at the time held by the Empire of Trebizond, one of the Byzantine Greek successor states formed after the Fourth Crusade. The siege is described in some detail by the near-contemporary Seljuq chronicler Ibn Bibi. The Trapezuntine emperor Alexios I (r. 1204–1222) led an army to break the siege, but he was defeated and captured, and the city surrendered on 1 November.