The history of Denmark as a unified kingdom began in the 8th century, but historic documents describe the geographic area and the people living there—the Danes—as early as 500 AD. These early documents include the writings of Jordanes and Procopius. With the Christianization of the Danes c. 960 AD, it is clear that there existed a kingship. King Frederik X can trace his lineage back to the Viking kings Gorm the Old and Harald Bluetooth from this time, thus making the Monarchy of Denmark the oldest in Europe. The area now known as Denmark has a rich prehistory, having been populated by several prehistoric cultures and people for about 12,000 years, since the end of the last ice age.
Denmark's history has particularly been influenced by its geographical location between the North and Baltic seas, a strategically and economically important placement between Sweden and Germany, at the center of mutual struggles for control of the Baltic Sea (dominium maris baltici). Denmark was long in disputes with Sweden over control of Skånelandene and with Germany over control of Schleswig (a Danish fief) and Holstein (a German fief).