two phases. Ian Howard theorises that the death of Svein Knutsson could have strengthened Harold's position. He went from being the second surviving son of Cnut to being the eldest living, with Harthacnut still absent and unable to press his claim to the throne. Harold himself is somewhat obscure; the historian Frank Stenton considered it probable that his mother Ælfgifu was "the real ruler of England" for part or all of his reign. Kelly DeVries points out that during the High Middle Ages, royal succession in Northern Europe was determined by military power. The eldest son of a king could have a superior right of inheritance but still lose the throne to a younger brother, or other junior claimant, possessing greater military support. Harold managed to win the throne against the superior claim of Harthacnut in this way. The 11th century provides other similar examples. Magnus I of Norway (reigned 1035–1047), who wasn't a warlord, had reigned for more than a decade when his uncle Harald Hardrada (reigned 1047–1066) challenged his rule. With Harald being a famous military leader, his claim would end Magnus' reign early. Baldwin VI, Count of Flanders (reigned 1067–1070) was effectively succeeded by his brother Robert I (reigned 1071–1093), rather than his own sons. Robert Curthose, Duke of Normandy (reigned 1087–1106) lost the throne of England to his younger brothers William II (reigned 1087–1100) and Henry I (reigned 1100–1135). With the Kingdom of England practically owned by Harold, Harthacnut could not even approach without securing sufficient military strength. His decision to remain in Denmark probably points to him lacking sufficient support, though he would certainly wait for an opportunity to forcefully assert his claim and depose his half-brother. Harold reigned as sole king from 1037 to 1040. There are few surviving documents about events of his reign. The Anglo-Saxon Chronicle mostly covers church matters, such as the deaths and appointments of bishops and archbishops. There is, however, record of a skirmish between the Anglo-Saxons and the Welsh in 1039. The named casualties were Eadwine (Edwin), brother to Leofric, Earl of Mercia, Thurkil, and Ælfgeat, but there are no other details concerning this event. Also in 1039, there is mention of a great gale, again with no details. Return of Ælfred and Edward In 1036, Ælfred Ætheling, son of Emma by the long-dead Æthelred, returned to the kingdom from exile in the Duchy of Normandy with his