Question: Strut-Harald was a king who ruled over what North Germanic tribe of southern Scandinavia?

full_context: Document 1: Vikings: Vikings (Old English: "wicing"—"pirate", Danish and Bokmål: "vikinger" ; Swedish and Nynorsk: "vikingar" ; Icelandic: "víkingar" , from Old Norse "víkingar "), were Norse seafarers, mainly speaking the Old Norse language, who raided and traded from their Northern European homelands across wide areas of northern, central and eastern Europe, during the late 8th to late 11th centuries. The term is also commonly extended in modern English and other vernaculars to the inhabitants of Viking home communities during what has become known as the Viking Age. This period of Nordic military, mercantile and demographic expansion constitutes an important element in the early medieval history of Scandinavia, Estonia, the British Isles, France, Kievan Rus' and Sicily.
Document 2: Sigtryg Eysteinsson: Sigtryg Eysteinsson was king of the Norwegian petty kingdoms Raumarike and Hedmark in what is today south-eastern Norway. He was killed by Halfdan the Black ("Halvdan Svarte") in the middle of the 9th century. Halfdan the Black subdued the area by first defeating and killing Sigtryg in battle and then defeated Sigtryg's brother and successor Eystein Eysteinsson in a series of battles.
Document 3: Norse–Gaels: The Norse–Gaels (Old Irish: "Gall-Goídil" , Irish: "Gall-Ghaedheil" or "Gall-Ghaeil ", Scottish Gaelic: "Gall-Ghàidheil" , "foreigner Gaels") were a people of mixed Gaelic and Norse ancestry and culture. They emerged in the Viking Age, when Vikings who settled in Ireland and in Scotland adopted Gaelic culture and intermarried with Gaels. The Norse–Gaels dominated much of the Irish Sea and Scottish Sea regions from the 9th to 12th centuries. They founded the Kingdom of the Isles (which included the Hebrides and the Isle of Man), the Kingdom of Dublin, the Lordship of Galloway (which is named after them), and ruled the Kingdom of York for a time. The most powerful Norse–Gaelic dynasty were the Uí Ímair or House of Ivar.
Document 4: Kings of the Angles: The Angles were a dominant Germanic tribe in the Anglo-Saxon settlement of Britain, and gave their name to the English, England and to the region of East Anglia. Originally from Angeln, present-day Schleswig-Holstein, a legendary list of their kings has been preserved in the heroic poems "Widsith" and "Beowulf", and the "Anglo-Saxon Chronicle".
Document 5: Strut-Harald: Strut-Harald ("Cone Harald" from his cone-shaped helmet of gold) was a semi-legendary jarl or petty king who ruled over the Danish territory of Scania (in what is now southern Sweden) during the late 10th century CE (approximately 975-986). Norse sagas identify him as the son of Gorm the Old, His Sister being Astrid Wiffen who was married to the Earl Philippus Sigefrid Wiffen of Scania, Strut-Harald was also a half-brother of Harald Bluetooth.
Document 6: Quadi: The Quadi were a Suebian Germanic tribe who lived approximately in the area of modern Moravia in the time of the Roman empire. The only known information about the Germanic tribe the Romans called the 'Quadi' comes through reports of the Romans themselves, whose empire had its border on the River Danube just to the south of the Quadi. They associated the Quadi with their neighbours the Marcomanni, and described both groups as having entered the region after the Celtic Boii had left it deserted. The Quadi are thought to have been an important part of the Suebian group who crossed the Rhine with the Vandals and Alans in the 406 Crossing of the Rhine, and later founded a kingdom in northwestern Iberia.
Document 7: Saxons: The Saxons (Latin: "Saxones" , Old English: "Seaxe" , Old Saxon: "Sahson" , Low German: "Sassen" , German: "Sachsen" , Dutch: "Saksen" , Welsh: "Saeson" ) were a group of Germanic tribes first mentioned as living near the North Sea coast of what is now Germany (Old Saxony), in the late Roman empire. They were soon mentioned as raiding and settling in many North Sea areas, as well as pushing south inland towards the Franks. Significant numbers settled in large parts of Great Britain in the early Middle Ages and formed part of the merged group of Anglo-Saxons who eventually organised the first united Kingdom of England. Many Saxons however remained in Germania (Old Saxony c. 531-804), where they resisted the expanding Frankish Empire through the leadership of the semi-legendary Saxon hero, Widukind. Initially, Saxons of Britain and those of Old Saxony (Northern Germany) were both referred to as 'Saxons' in an indiscriminate manner. The term Anglo-Saxon, in turn, came into practice in the 8th century (probably by Paul the Deacon) to distinguish English Saxons from continental Saxons (Ealdseaxe, 'old Saxons').
Document 8: Ragnvald Heidumhære: Ragnvald Heidumhære (or Rognvald) was a legendary, possibly historic, petty king or chieftain of Vestfold in what is today Norway in the 9th century, according to "Ynglingatal" and to "Ynglinga saga" in "Heimskringla". He was the son of Ragnar Lodbrok or Olaf Geirstad-Alf. His name "Heiðumhæri" could be translated as "highly honoured"
Document 9: Harald Bluetooth: Harald "Bluetooth" Gormsson (Old Norse: "Haraldr Gormsson" , Danish: "Harald Blåtand Gormsen" , died c. 985/86) was a king of Denmark and Norway.
Document 10: Halfdan the Black: Halfdan the Black (Old Norse: "Halfdanr Svarti") (  810 –  860 ) was a ninth-century king of Vestfold. He belonged to the House of Yngling and was the father of Harald Fairhair, the first king of Norway.
Document 11: Great Heathen Army: The Great Viking Army or Great Danish Army, known by the Anglo-Saxons as the Great Heathen Army (OE: "mycel hæþen here"), was a coalition of Norse warriors, originating from Denmark (and likely also from Sweden and Norway) who came together under a unified command to invade the four Anglo-Saxon kingdoms that constituted England in AD 865.
Document 12: Halfdan Haraldsson the Black: Halfdan Haraldsson or Halfdan the Black (not to be confused with his grandfather and namesake) was a son of Harald I of Norway by his first wife, Åsa, the daughter of Jarl Håkon Grjotgardsson of Lade. He was made sub-king of the Trondelag by his father, along with his brother Halfdan the White. According to "Heimskringla", Halfdan the Black was poisoned, possibly at the behest of his sister in law Gunnhild, Mother of Kings.
Document 13: Geography of Denmark: Denmark is a Nordic country located in Northern Europe. It consists of the Jutland peninsula and several islands in the Baltic sea, referred to as the Danish Archipelago. Denmark is located southwest of Sweden and due south of Norway and is bordered by the German state (and former possession) Schleswig-Holstein to the south, on Denmark's only land border, 68 kilometres (42 miles) long.
Document 14: Olaf Geirstad-Alf: Olaf Gudrødsson, or as he was named after his death Olaf Geirstad-Alf (Old Norse Ólaf Geirstaða Álfr), was a legendary Norwegian king of the House of Yngling from the "Ynglinga saga". He was the son of Gudrød the Hunter and according to the late "Heimskringla", the half-brother of Halfdan the Black. Gudrød and Olaf conquered a large part of Raumarike.
Document 15: Danes (Germanic tribe): The Danes were a North Germanic tribe inhabiting southern Scandinavia, including the area now comprising Denmark proper, during the Nordic Iron Age and the Viking Age. They founded what became the Kingdom of Denmark. The name of their realm is believed to mean "Danish March", viz. "the march of the Danes" in Old Low German, referring to their southern border zone between the Eider and Schlei rivers.
ground_truth: Danes