TIL Byzantine emperors hired Vikings as guards. One of whom, Halfdan, left runic graffiti on the Hagia Sophia.

https://en.wikipedia.org/wiki/Runic_inscriptions_in_Hagia_Sophia
#til #todayilearned
https://www.reddit.com/r/todayilearned/comments/1g9e03r/til_byzantine_emperors_hired_vikings_as_guards/