A member of the extended imperial family, Alexios came to the throne after deposing, blinding and imprisoning his younger brotherIsaac II Angelos. The most significant event of his reign was the attack of theFourth Crusade onConstantinople in 1203, on behalf ofAlexios IV Angelos.
Alexios III took over the defence of the city, which he mismanaged, and then fled the city at night with one of his three daughters. FromAdrianople, and thenMosynopolis, he attempted unsuccessfully to rally his supporters, only to end up a captive of MarquisBoniface of Montferrat. He was ransomed and sent to Asia Minor where he plotted against his son-in-lawTheodore I Laskaris, but was eventually captured and spent his last days confined to the Monastery of Hyakinthos inNicaea, where he died.
His younger brotherIsaac II was threatened with execution under orders of Andronikos I, their first-cousin once-removed, on 11 September 1185. Isaac made a desperate attack on the imperial agents and soon killed their leaderStephen Hagiochristophorites. He then took refuge in the church ofHagia Sophia and from there appealed to the populace. His actions provoked a riot, which resulted in the deposition of Andronikos I and the proclamation of Isaac as Emperor. Alexios was now closer to the imperial throne than ever before.
By 1190 Alexios had returned to the court of his younger brother, from whom he received the elevated title ofsebastokratōr. In March 1195 while Isaac II was away hunting inThrace, Alexios was acclaimed as emperor by the troops with the covert support of his wifeEuphrosyne Doukaina Kamatera. Alexios captured Isaac atStagira inMacedonia,put out his eyes, and thenceforth kept him a close prisoner, despite having previously been redeemed by Isaac from captivity atAntioch and showered with honours.[3]
To compensate for this crime and to solidify his position as emperor, Alexios had to scatter money so lavishly as to empty his treasury, and to allow such licence to the officers of the army as to leave the Empire practically defenceless. These actions inevitably led to the financial ruin of the state. At Christmas 1196, Holy Roman EmperorHenry VI attempted to force Alexios to pay him a tribute of 5,000 pounds (later negotiated down to 1,600 pounds) of gold or face invasion. Alexios gathered the money by plundering imperial tombs at the church of the Holy Apostles and heavily taxing the people through theAlamanikon. Because of Henry's death in September 1197, the gold was never dispatched. The Empress Euphrosyne tried in vain to sustain his credit and his court; Vatatzes, the favourite instrument in her attempts at reform, wasassassinated by the emperor's orders.[3]
In the east the Empire was overrun by theSeljuk Turks; from the north, theKingdom of Hungary and the rebelliousBulgarians andVlachs descended unchecked to ravage the Balkan provinces of the Empire, sometimes penetrating as far as Greece, while Alexios squandered the public treasure on his palaces and gardens and attempted to deal with the crisis through diplomatic means. The Emperor's attempts to bolster the empire's defences by special concessions topronoiai (notables) in the frontier zone backfired, as the latter increased their regional autonomy. Byzantine authority survived, but in a much weakened state. In 1197, local lordDobromir Chrysos established himself in the region ofVardar Macedonia, defying the imperial power for several years.[4]
During the first years of Alexios' reign, relations between Byzantium andSerbia were good, since his daughterEudokia Angelina was married to Serbian Grand PrinceStefan Nemanjić II, who was granted the title ofsebastokrator. But in 1200, those relations deteriorated. The marriage between Stefan and Eudokia was dissolved, and the alliance between Serbia and Byzantium ended, leaving Byzantium without a single ally in Southeastern Europe.[5][6]
Soon, Alexios was threatened by a new and more formidable danger. In 1202, soldiers assembled atVenice to launch theFourth Crusade.Alexios IV Angelos, the son of the deposed Isaac II, had recently escaped fromConstantinople and now appealed for support to the crusaders, promising to end theEast–West Schism, to pay for their transport, and to provide military support if they would help him depose his uncle and ascend to his father's throne.[3]
The crusaders, whose objective had beenEgypt, were persuaded to set their course for Constantinople, arriving there in June 1203, proclaiming Alexios IV as emperor, and inviting the populace of the capital to depose his uncle. Alexios III took no effective measures to resist, and his attempts to bribe the crusaders failed. His son-in-law,Theodore I Laskaris, who was the only one to attempt anything significant, was defeated atScutari, and the siege of Constantinople began. Misgovernment by Alexios III had left theByzantine navy with only 20 worm-eaten hulks by the time the crusaders arrived.[citation needed]
In July, the crusaders, led by the agedDogeEnrico Dandolo, scaled the walls and took control of a major section of the city. In the ensuing fighting, the crusaders set the city on fire, ultimately leaving 20,000 people homeless. On 17 July, Alexios III finally took action and led 17 divisions from theGate of St. Romanus, vastly outnumbering the crusaders. His courage failed, however, and the Byzantine army returned to the city without a fight. His courtiers demanded action, and Alexios III promised to fight. Instead, that night (17/18 July), Alexios III hid in the palace, and finally, with one of his daughters, Eirene, and as much treasure (1,000 pounds of gold) as he could collect, got into a boat and escaped toDeveltos in Thrace, leaving his wife and his other daughters behind. Isaac II, drawn from his prison and robed once more in the imperial purple, received his son, Alexios IV, in state.
Alexios III attempted to organize resistance to the new regime fromAdrianople and thenMosynopolis, where he was joined by the later usurperAlexios V Doukas in April 1204, after the definitivefall of Constantinople to the crusaders and the establishment of theLatin Empire. At first, Alexios III received Alexios V well, even allowing him to marry his daughterEudokia Angelina. Later, Alexios V was blinded and deserted by his father-in-law, who fled from the crusaders intoThessaly. Here Alexios III eventually surrendered, with Euphrosyne, to MarquisBoniface of Montferrat, who was establishing himself as ruler of theKingdom of Thessalonica.