Although some flags date back earlier, widespread use of flags outside of military or naval context begins only with the rise of the idea of the nation state at the end of the 18th century and particularly are a product of the Age of Revolution. Revolutions such as those in France and America called for people to begin thinking of themselves as citizens as opposed to subjects under a king, and thus necessitated flags that represented the collective citizenry, not just the power and right of a ruling family.[61][62] With nationalism becoming common across Europe in the 19th century, national flags came to represent most of the states of Europe.[61] Flags also began fostering a sense of unity between different peoples, such as the Union Jack representing a union between England and Scotland, or began to represent unity between nations in a perceived shared struggle, for example, the Pan-Slavic colors or later Pan-Arab colors.[63]