These days I wrote and spoke a lot about Basij militia (paramilitary group backed by revolutionary guards. Basiji means a Basij member) but we need to examine them once again to see who exactly we are dealing with.
Back then I replied in response to the very same question:
Basij members believe that they are fulfilling god’s wish and they will be rewarded in this world and ultimately in heaven by Allah. They consider supreme leader, representative of Allah on earth. The question is, do they really think like this or just pretend to be like this? I guess the answer lies in the degree of indoctrination, there are many among them that would kill people if they get orders and there are some others just to gain benefits.
Following video is old but still gives you an idea of Basij perspective:
Now the violence that we have seen in the aftermath of Iran election crisis has done by Basij members are just tips of iceberg. These people are ready to do anything that their leader, supreme leader would order them as their religious duty. They do get bonus for their total obedience, and also they believe they will be awarded in heaven because they are carrying out Allah’s wish. The latter one indeed is the motivational push to kill, beat and torture civilian people.
In following video shows a group of Basij militia bikers heading to suppress protesters. In the vidoe, we can see that they carry club, rod and chain. They are usually armed with firearms too.
If I want to simply define Basij militia I would say they are extremely brainwashed slave of clergy man.