On 25 July 1261 a Byzantine force of about eight hundred men walked into Constantinople through an undefended gate while the Latin fleet was away. The empire was restored without a battle.
The Byzantine recovery of Constantinople was not a siege, a battle or a campaign. It was a reconnaissance that found the door open.
In July 1261 Alexios Strategopoulos was moving through Thrace with a small force — the sources say around eight hundred men, mostly Cuman horse archers — with orders to observe the city, not to attack it.
Local Greeks told him the garrison and the entire Venetian fleet had sailed to attack the island of Daphnousia in the Black Sea. On the night of 24–25 July his men entered through an undefended postern, opened a gate from inside, and by morning the city was theirs.
Fifty-seven years of Latin rule had reduced Constantinople to a shell. The Latin emperors had sold the relics — the Crown of Thorns went to Louis IX of France, who built the Sainte-Chapelle to house it — and stripped the lead from the palace roofs to pay their debts. The population had collapsed.
What kept the city Latin was Venetian sea power, and Michael VIII removed it diplomatically. By the Treaty of Nymphaeum in March 1261 he gave Genoa the commercial privileges Venice had held, in exchange for Genoese ships.
Pelagonia in 1259 had already destroyed the land coalition. By the summer of 1261 there was nothing left protecting the city except the fleet, and the fleet went to Daphnousia.
The Greeks inside the city had kept contact with Nicaea, and it was they who told Strategopoulos the fleet was gone and showed his men the postern.
A party went over or through the wall, killed the watch, and opened one of the gates. The Latin garrison, such as it was, could not organise a defence of a four-mile land wall with the men remaining.
The emperor Baldwin II fled to the harbour, abandoning his crown and sword in the palace, and took ship for Euboea. The Venetian quarter was burned to prevent the fleet returning to a base, and the Latin population fled with it. The fleet came back to find the city gone.
The emperor was camped in Asia Minor and heard the news three weeks later. He entered Constantinople on 15 August, the feast of the Dormition, walking behind an icon of the Virgin — the same association the deliverance of 626 had used, and deliberately so.
He was crowned in Hagia Sophia, which had been a Latin cathedral for two generations. The city he inherited was half-empty and ruinous, and he spent the rest of his reign repopulating and rebuilding it.
At Christmas 1261 he had John IV Laskaris — the eleven-year-old legitimate emperor of Nicaea, in whose name he had first taken power — blinded and imprisoned. The patriarch Arsenios excommunicated him for it, and the schism that followed divided the church for decades.
The restoration is the last great reversal in Byzantine history and it is genuinely astonishing: an empire that had ceased to exist in 1204 recovered its capital fifty-seven years later with eight hundred men and no fighting.
It also inherited an impossible position. The empire that returned to Constantinople was a fraction of the one that had left it, surrounded by hostile Latin states, committed to defending a capital far too large for it, and dependent on Genoese sea power it did not control.
Michael VIII spent his reign holding the west off by diplomacy — the church union of 1274, the encouragement of the Sicilian Vespers in 1282 — while Anatolia, the empire's recruiting ground, was left to the Turkish frontier lords. The Ottoman emirate that would end the empire took shape there within a generation of his death.