Toynbee, Arnold J. "The Forfeited Birthright of the Abortive Scandinavian Civilization"
Divergence: 860 CE
What if: The Vikings captured Constantinople in 860, established stronger colonies in North America, harassed the Muslims in the Caspian, etc.
Comments: How more aggressive expansion would have resulted in Viking control of North America, Europe and northern Asia by 1400.
Published: In A Study of History, Volume II, Oxford University 1934 (0192152084w88 android).