The Red Cross is teaching Palestinian gunmen international rules of war. The BBC sat in on a class:
Mr Nasr told me how surprised some of the gunmen were to find that groups like theirs have a status under international law.
“But then they also have to realise they have responsibilities. Legal ones. And if they don’t keep them, they can be prosecuted under international law.
“And that comes as quite a surprise to these guys, most of whom have always viewed themselves as the victims.”