The castle was owned by some people who
were good at assassination (ancient terrorists).
They killed people around and soon annoyed
Salah ad-Din.
So Salah ad-Din siege the castle.
In the midst of his camp,
Surrounded by his personal guard, Salah
ad-Din woke suddenly one evening
to see a shadowy figure
slip out of his tent
and found
at the foot of his bed a dagger and
a note of warning from the
leader of the assassins.
Some sort of agreement must have been reached between the two parties
because Salah ad-Din soon stopped the siege.