Harald Sigurdsson (Old Norse: Haraldr Sigurðarson; c. 1015 – 25 September 1066), also known as Harald III of Norway and given the epithet Hardrada in the sagas, was King of Norway from 1046 to 1066. He unsuccessfully claimed the Danish throne until 1064 and English throne in 1066. Before becoming king, Harald spent 15 years in exile as a mercenary and military commander in Kievan Rus' and chief of the Varangian Guard in the Byzantine Empire. In his chronicle, Adam of Bremen called him the "Thunderbolt of the North".
https://en.wikipedia.org/wiki/Harald_Hardrada