The first indubitable king's name in historic sources crops up in connection with the earliest known mission in Denmark in the early 700s. At that time the English missionary Willibrord, archbishop of Utrecht, visited the tribe of the wild Danes. About this the legend says: This is where Ongendus (probably a Latin version of the Nordic name Angantyr) is to have reigned, a man more cruel than a wild beast and harder than stone, but according to God's will he did treat the preacher of truth honourably. This may be the very same Ongendus who founded the town of Ribe.

There is much to indicate that already in the early 700s a strong central power prevailed in Denmark, at least in Jutland. The oldest phase of the great defence rampart in the south the Danevirke dates back to the year 737, and in 726 a one kilometre long wood­lined canal was established across the narrowest part of the island of Sams for the purpose of controlling navigation in the Danish belts. Projects of this magnitude must have required a firm organisation.

Throughout the 800s Frankish sources provide sporadic news about Danish kings. We have already mentioned King Godfred who founded Hedeby in 808 and who was sufficiently powerful to threaten Charlemagne. Other kings mentioned are Horik the Older and Horik the Younger who in the 850s allowed the missionary Ansgar to build churches in both Hedeby and Ribe. But it is only in the mid­900s that we have adequate information to observe a coherent list of kings.

The territory which was later to constitute medieval Denmark was to all appearances more or less unified around the year 800. One thing is sure, namely that by the early 800s King Godfred reigned not only over Jutland but also over southern Norway and Scania.

The designation Denmark (Danmark) originates from the Danes the tribe of the savage Danes as they are referred to in connection with the visit of Willibrord the missionary. The name Denmark is used the first time in the travel descriptions of Ottar and Wulfstan as these committed them to paper at the English court during the second half of the 800s. Ottar lived in northern Norway and travelled northwards by ship around the North Cape and into the White Sea, and southwards to the trading place Skiringssal on the Oslo Fjord and then on to Hedeby. Part of Ottar's account reads: And he said that from Skiringssal it took him five days to sail to the commercial town of Hedeby. It is located between the Wends, the Saxons and the Anglians; to port was Denmark, to starboard the open sea for three days; and then, two days before arriving at Hedeby, he had Jutland and Sillende and many isles to starboard. This is where the Anglians lived before settling in this country (NB! the travel accounts were told in England). And during these two days he had the Danish isles to port.

Wulfstan tells about a voyage from Hedeby to the town of Truso on the estuary of the Weichsel river in what is today Poland. Among Wulfstan 's accounts: He left from Hedeby, reached Truso in seven days and nights, and the ship set sail the whole trip. The land of the Wends was to starboard while to port were Langeland, Lolland, Falster and Scania. These territories all belong to Denmark.

The Wends mentioned by Wulfstan were the neighbours of the Danes to the south on the Baltic Sea. The land was inhabited by a number of West Slav tribes which in the 6­700s had penetrated from eastern Europe to the Baltic Sea and with whom the Danes alternated between belligerent and peaceful contacts.

By the mid­900s Gorm the Old was king of Denmark.

Harald's runic stone has been called the baptismal certificate of Denmark and is the official farewell of Denmark to the ancient gods. This faith in gods has been alleged by the missionaries arriving from the south; they fancied the designations heathens and wild barbarians about non­Christians. However, the most important written sources for the understanding of the Nordic mythology are the so­called Edda Poems: the elder Edda collected around the year 1200 by an anonymous Icelander, and the younger Edda by Snorre in the early 1200s. Snorre describes the mythology as a whole which begins with genesis and ends with ragnarok, the doom of the world. Odin is the august principal god while among the other gods Thor is especially prominent. Odin was the god of war and the paradise of the Viking warrior was Valhalla where time was spent on noble battle and feast. The most favoured god seems to have been Thor, however. Thor is invoked on the runic stones: To Thor be devoted these runes. The name of Thor recurs in many local names and his hammer was a popular motif on jewellery. Thor was also a warrior god who showed himself in thunder: Thor crash. Undoubtedly noble battle ranked among the finest virtues of the Vikings.

Conversion to Christendom was hardly very sudden since missionaries had been active in Denmark for more than 200 years; nor does the conversion of faith appear to have reduced the lust for battle.

In addition to the famous runic stone Harald built two colossal mounds: kings graves, and a church in Jelling. Most likely Harald was also the promoter of the construction of the four large circular castles strategically placed in various locations in Denmark. The common feature of the castles was the circular ramparts protecting a barracks­like military installation.