The Latin Principality of Achaea had held most of the Morea — the Peloponnese — for over a century when the Battle of Saint George took place. But by 1320, the principality was in serious trouble. The princely succession had been contested for years: a Catalan invasion in support of Isabella of Sabran had been defeated at the Battle of Manolada in 1316, but the crisis of succession continued, with claims disputed between Matilda of Hainaut, the Angevin House of Naples, and Odo IV, Duke of Burgundy. An Angevin governor, Frederick Trogisio, had been sent to administer the principality in 1318, but the underlying instability was unresolved.

While the Principality fractured, the Byzantine province of Mystras — covering the southeastern Morea — had come under the capable governance of Andronikos Asen, a nephew of the Byzantine emperor Andronikos II Palaiologos. From 1316 onward, Asen pursued the war against the Latins with sustained energy. Arcadia, the central highland plateau of the Morea, was his primary objective.

In 1320, Asen launched a campaign into Arcadia. His target was the castle of Saint George in Skorta — a fortress the Latins had built in the early 1290s as part of a chain protecting the mountain passes. The Chronicle of the Morea, preserved in French and Aragonese versions, describes what happened next.

Asen besieged the castle, and as the Latin baillie Trogisio assembled a relief force — calling on the Bishop of Olena, James of Cyprus, Grand Constable Bartholomew II Ghisi, and the commanders of the Knights of St. John and the Teutonic Knights — Asen intensified his pressure on the garrison. On 9 September, the Greek castellan, Nicoloucho of Patras, surrendered the castle to him. Asen immediately had the Achaean banners left flying. When the Latin relief column approached through the mountain passes, they saw the familiar flags and assumed their allies still held the fortress. Asen waited until they were committed. Then the Byzantines struck.

The battle that followed was a decisive Byzantine victory. Many Latin soldiers died in the ambush, including the commander of the Teutonic Knights. Among the captured were Bartholomew Ghisi and the Bishop of Olena. The Bishop was released immediately; Ghisi and the others were taken to Constantinople.

Asen's 1320 campaign did not end with Saint George. In the same operation — the sources disagree on the precise sequence — the Byzantines acquired, through bribes to their commandants, three additional castles: Karytaina, Akova, and Polyphengos. These fortresses had formed the backbone of Latin defensive power in the Arcadian mountains for fifty years.

The loss was catastrophic for the Principality of Achaea. With these fortresses gone, the principality was effectively reduced to the western and northern coastal regions of the Morea: Messenia, Elis, Achaea, Corinthia, and Argolis. The Arcadian plateau — the heartland of the peninsula — now belonged to Byzantium. Many Latin settlers who remained in Arcadia, some of whom had Greek mothers, abandoned the Catholic Church and converted to Greek Orthodoxy. The cultural landscape of the region shifted accordingly.

The shock of Asen's campaign was severe enough that the leading barons of the principality sent a Franciscan prior, Peter Gradenigo, to the Doge of Venice in June 1321, offering to place the principality under Venetian sovereignty. Venice declined. The Angevins sent a new baillie, Ligorio Guindazzo, who served for roughly a year without reversing the Byzantine gains.

John of Gravina, the Angevin prince who held the title to Achaea, finally arrived with a force of 25 galleys, 400 cavalry, and 1,000 infantry in January 1325. He re-established Angevin control over what remained of the principality, but his attempt to retake Karytaina failed against its Byzantine garrison. In spring 1326 he departed again. The Duke of Naxos, Nicholas I Sanudo, won a local victory against a Byzantine raiding force shortly afterward, but it was not enough to reverse the strategic situation. The Battle of Saint George had decided the question of who held Arcadia, and that decision proved durable.

The castle of Saint George in Skorta stood in the Arcadian mountain region at approximately 37.441°N, 22.019°E, in the rugged interior of the Peloponnese. The terrain here is steep and heavily dissected — a landscape of narrow valleys and rocky ridgelines that made these mountain fortresses genuinely formidable and made the Byzantine tactic of ambush in the passes highly effective. The nearest major airport is LGKL (Kalamata International), roughly 60 kilometers to the southwest. Approach from the west at 6,000–8,000 feet; the Arcadian mountain landscape is striking from altitude, its peaks and passes visible in the clear air that characterizes the Peloponnese in autumn, when the 1320 battle took place.