You all know why…
The Comet Cometh
What Vlad actually did,
is he took out all the traitors who showed support for the muslims, and he impaled them and their families.
As the muslims approached, it eventually dawned on them that all their "friends" were gone. and they were going to have to fight a battle without the traitors on the inside, so they went back home.
Be like Vlad.