
Here’s another great post from the genetic genealogy blog Origin Hunters.
European crusaders in the early medieval era…The real question is not if they left DNA behind. There is significant literature that details the atrocities; raping and pillaging was standard operating procedure for the Crusaders. There are also numerous accounts of assimilation.

During the Crusaders’ 247-year occupation – and roughly eight generations – they married local women and raised families. The real question is did Crusader DNA survive to modern time
This is an interesting read to say the least.
Atrocities and Assimilation: Crusader DNA in the Near East:
http://originhunters.blogspot.com/2014/12/atrocities-and-assimilation-crusader.html