"He is probably the first to spell out a doctrine for a decentralised global jihad," said Brynjar Lia, a counterterrorism researcher at the Norwegian Defence Research Establishment, who is writing a book on Nasar.

"In my humble opinion, he is the best theoretician among the jihadi ideologues and strategists out there. Nobody is as systematic and comprehensive in their analysis as he is. His brutal honesty and self-criticism is unique in jihadi circles."