When the Fourth Crusade's armies stormed Constantinople in April 1204, they did not merely defeat a city. They dismembered an empire that had endured for nearly nine centuries. Byzantine rule collapsed across large parts of Anatolia and Greece virtually overnight, replaced by a patchwork of Crusader lordships, Greek successor states, and disputed territories. The Latin Empire of Constantinople — with Baldwin of Flanders as its first emperor — was the largest of these new entities, but it was fragile. Byzantine resistance coalesced particularly in the Empire of Nicaea, established by Theodore I Laskaris in northwestern Anatolia.

The Nicaean state was the legitimate heir of Byzantine political and ecclesiastical tradition in the view of most Greeks, and Theodore worked quickly to consolidate it. But consolidation required pushing back against Latin expansion. Along the Aegean coast, cities like Adramyttion — which had been Byzantine for centuries — became contested ground. Henry of Flanders was the Latin commander attempting to hold and extend that coastline.

According to Geoffrey de Villehardouin, the French knight and chronicler who was present at the Fourth Crusade, Henry of Flanders was encouraged by Armenian contacts to move on Adramyttion. He departed from Abydos, left a garrison in place, and rode for two days before encamping outside the city. Adramyttion surrendered without significant resistance, and Henry occupied it as a forward base from which to pressure the Nicaean forces.

Theodore Laskaris, still troubled by an earlier defeat, assembled as large an army as he could from around Nicaea and dispatched it to Adramyttion under the command of his brother Constantine. Henry, warned by his Armenian contacts that a large Byzantine force was approaching, prepared what forces he had. When Constantine appeared before the walls on 19 March 1205, Henry made the decision not to wait behind them. He opened the city gates and rode out with his heavy cavalry. The fighting was close and fierce. Henry's cavalry prevailed. Much of the Byzantine force was killed or captured, and the Latins took a substantial quantity of weapons and treasure.

Niketas Choniates, the Byzantine historian who wrote the other major account of this period, told a substantially different story. In his version, the Byzantine commander was not Constantine Laskaris but Theodore Mangaphas — a usurper who controlled the city of Philadelphia and had his own ambitions in the region. Mangaphas had learned of a recent Byzantine victory against the Latins and marched against Henry with confidence, surprising him with the size of his forces.

Henry, according to Choniates, was alarmed — convinced he faced a desperate situation and had no choice but to attack. He drew up his cavalry, couched their lances, and personally led the charge, riding through the centre of the Byzantine formation. His cavalry followed, raising the war cry. The Byzantine horsemen fled, abandoning their infantry. Many of those who remained were cut down; others were taken prisoner. The human cost on the Byzantine side was severe.

The two accounts agree on the outcome — a Latin victory, significant Byzantine losses — but differ on who the Byzantine commander was and on the character of the engagement. Most subsequent historians have suggested there may have been two separate engagements: one against Constantine Laskaris, which failed, and a second against Theodore Mangaphas, both occurring within a short period in early 1205.

The battle at Adramyttion did not settle the question of who controlled this stretch of the Aegean coast. Adramyttion was recovered by the Empire of Nicaea later in 1205, held until 1211, then retaken by Henry of Flanders following his victory over Theodore I Laskaris at the Battle of the Rhyndacus. A subsequent treaty, the Treaty of Nymphaeum, formally ceded Adramyttion to the Latin Empire. Latin rule in Anatolia collapsed entirely in 1224, and the Empire of Nicaea reclaimed the city.

The wars of the early 13th century along this coast involved not just battles but populations — Byzantine Greek civilians, Latin garrisons, Armenian merchants, Genoese traders — all caught in a contest between political orders. The people of Adramyttion and the surrounding countryside experienced repeated changes of overlord, each bringing different legal and fiscal arrangements, different languages in the administrative records, different levels of security or insecurity. For ordinary residents, the Battle of Adramyttion was one episode in a generation of upheaval.

What the Battle of Adramyttion leaves us with is an unusually vivid illustration of how medieval military history was made and preserved. Villehardouin was a participant in the Fourth Crusade, writing in Old French from memory and personal experience, proud of the enterprise he had been part of. Choniates was a Byzantine imperial official who watched the empire he served destroyed, writing in Greek from the perspective of the defeated. Each shaped his account by what he knew, who he was, and what he needed the story to mean.

They agreed that men died at Adramyttion on 19 March 1205. They agreed the Latins won. On almost everything else — the commanders, the numbers, the sequence of events — they diverged. History, as usual, is the argument between the sources.