The Swedish Flag dates back to the 16th century and is believed to be inspired by the Coats of Arms of Sweden which feature three yellow crowns on a blue background, and is probably based on the Danish flag. In 1569, as decreed in a Royal warrant, the yellow cross was always to be borne on Swedish battle standards and banners. Evidence of the blue flag with a yellow cross being used by Swedish vessels is to be found in the 1620's, during the reign of Gustav II Adolf.