Denmark–Sweden relations relate to Denmark and Sweden. These two countries have a very long history of interaction. The inhabitants of each speak related North Germanic languages, which have a degree of mutual intelligibility. Both countries formed part of the Kalmar Union between 1397 and 1523, but there exists an inherited cultural competition between Sweden and Denmark. From 1448 to 1790 the two kingdoms went to war against each other at nearly every opportunity; in more than one case a new king tried to prove his worth by waging war on the other country for little or no political reason. Eleven Dano-Swedish wars took place between 1521 and 1814.