He was the Harald that won for himself all of Denmark and Norway and made pagans Christian, and that is fairly easy to read, but what did he exactly say? What does it meant when he says he won for himself all of Denmark? This has been a great matter of debate – did he reconquer territory that was lost? Did he, as many say, conquer Denmark? Or was it more a matter, this is the current belief, that he prevailed over other contenders to the throne?
Series of lectures on Viking "globalization" HERE.
That part that "Vikings were great traders"is a bit disingenuous: one of their main source of trade goods was slaves: Irish slaves to Islamic Spain, and Slavic slaves to Islamic Baghdad.