During medieval times, it was widely believed and taught that a pilgrimage to Jerusalem was the only way to atone for serious sins—and by serious, I mean murder and rape and such like. There was lots of sinning, so there were lots of pilgrims.
By the tenth century, many Norse pilgrims were coming [to Jerusalem] even though most of their countrymen were still pagans. “Most Scandinavian pilgrims liked to make a round tour, coming by sea through the Straits of Gibraltar and returning overland through Russia.” Like the Franks, the Norse converts were “very devoted to Christ if not to his commandments.” Among them was Thorvald the Far-Traveled, who came all the way from Iceland. Thorvald was a renowned Viking who had converted to Christianity and then “tried to preach the new faith to his countrymen in 981.” He undertook a pilgrimage in 990 seeking to atone for having killed two poets who had mocked his faith and another man who had criticized his preaching. Following his pilgrimage he devoted his missionary activities to Russia and died there, presumably without murdering any Russian pagans.
Just one of the intriguing tidbits from history in God’s Battalions: The Case for the Crusades by Rodney Stark.