How did the Scottish flag design become the Scottish flag?

The Scottish flag, known as the Saltire or St. Andrew's Cross, features a white cross on a blue background. Its design is rooted in the legend of St. Andrew, the patron saint of Scotland, who was crucified on a diagonal cross. According to tradition, the flag's design was first used in battle in the 9th century and became increasingly associated with Scottish identity over the centuries. Officially recognized in the 15th century, the Saltire has since become a symbol of Scotland's heritage and pride.