Harald 'Klak' Halfdansson (c. 785 – c. 852) was a king in Jutland (and possibly other parts of Denmark) around 812–814 and again from 819–827. Family The identity of Harald's father is uncertain. He had at least three brothers: Anulo (died 812), Ragnfrid (died 814) and Hemming Halfdansson (died 837). An 837 entry in the Annales Fuldenses calls Hemming a son of Halfdan. This is the only mention of their father in a primary source. The identification relies on the 'widely made assumption' that the Hemming mentioned in 837 was the same Hemming mentioned in chronicle entries from two decades before. Stewart Baldwin, a modern genealogist, pointed that they could also be two people with the same name, although Baldwin himself favors their identification. The relation of this Halfdan with other Danish rulers is also uncertain. An 812 entry in the Royal Frankish Annals mentions "Anulo nepos Herioldi". The Latin "nepos" can be translated as both "grandson" or "nephew", making Anulo and his siblings grandsons or nephews of a senior Harald. This would make Halfdan a brother or son of this Harald. The Frankish Annals vaguely mention this elder Harald as king. A late and unreliable source of Frisian history mentions that their king Redbad II (the last king of the Frisians) in 754 had to flee to "the land of the Danes" where king Harald reigned ("Daniae Regi Heraldi"). Also, a King Sigifrid (Siegfried) is mentioned in 777, granting refuge to the Saxon duke Widukind. In 782, an emissary by the name of Halfdan was sent by Sigifrid to Charlemagne. The last mention of Sigifrid in the Annals is in 798, when Charlemagne sent an envoy to him. In 804, Gudfred is mentioned as King of the Danes, exchanging envoys with Charlemagne. Harald could be related to Sigifrid and Gudfred. His reign occurring between 798 and 804 are placed prior to that of Sigifrid. The time and extent of the rule of these earlier kings are uncertain, but the area they ruled presumably included the region closest to the Frankish realm, i.e. around Hedeby. Although they are historical figures insofar as that they are mentioned in historical sources, the details of their rule mostly belong to the realm of the legendary Danish kings. The Europäische Stammtafeln: Stammtafeln zur Geschichte der Europäischen Staaten (1978) by Detlev Schwennicke assumes Sigifrid and the senior Harald to be brothers, both kings of Hedeby.