In the early 14th century, the power struggle in the region of Greece intensified, particularly within the context of the Duchy of Athens, a Crusader state established during the time of the Latin Empire. The Catalan Company, originally composed of Spanish mercenaries, had been invited to Greece to assist local rulers against a backdrop of turmoil and instability. On a significant day in March, the Catalan Company encountered the forces of Walter V, Count of Brienne, who was then the ruler of the Duchy of Athens.

The battle unfolded near the village of Halmyros, where Count Walter’s forces aimed to consolidate their control over Athens against the encroaching Catalan Company, which sought to expand its territory and influence. The engagement was marked by intense fighting, strategic maneuvers, and a well-coordinated assault by the Catalans, who ultimately overcame the Count’s forces. This victory was not merely a military achievement but a critical step towards establishing Catalan dominance in the region, paving the way for their rule over Athens.

Following the battle, the Catalan Company solidified its control over the Duchy and began to administer it effectively. Their rule significantly influenced the local culture and governance, intertwining Spanish and Greek elements. The aftermath of Halmyros established the Catalan Company as a dominant military and political power in Greece, changing the course of the region's history for years to come.