Why did European countries adopt flags linked to patron saints during the Middle Ages?

During the Middle Ages, European leaders adopted flags associated with their patron saint as a means of representation and identity. This practice emerged as flags became accepted symbols for countries, kings, and organizations toward the end of the medieval period.1

The adoption of these symbols was closely linked to the development of heraldry, which provided a system of identification for individuals and armies. In an era when most people were illiterate, these bold, simple designs allowed for the swift recognition of allies and foes on the battlefield, where distinguishing between different groups was essential. By aligning themselves with a patron saint—a figure believed to be a dedicated protector and intercessor—leaders sought to invoke divine protection while simultaneously establishing a clear, recognizable identity for their forces. A prominent example is the Cross of St. George, which was adopted as a symbol for England in the 13th century.213