Arguably, but I think you need more than that to make the argument. Al Qaeda, the parent organization achieved something similar in the 80s. The spanish civil

Arguably, but I think you need more than that to make the argument. Al Qaeda, the parent organization achieved something similar in the 80s. The spanish civil war in the 20s attracted international communists and anarchists (including George Orwell) to fight for their cause. Fascism spread across Europe very quickly. The radical liberalism of the French and American revolution is an earlier example. These ideas spread pretty fast. In all these cases (including ISIS) war was a major catalyst. In all cases propaganda played a major role and it was disseminated by whatever media was politically relevant at the time. Anticommunist revolutions of 1989 spread despite some pretty extreme centralization, censorship and control of media. Word gets around. You can also find many pre-modern and arguably ancient examples. FWIW, I believe a lot of ISIS propaganda was spread by cassette tape. For Al Qaeda, I believe this was the primary medium. In both cases, I seriously doubt that propaganda alone would have inspired and recruited so many. It was military success. ISIS recruits started arriving when they won Mosul. Once they crossed into Syria and established bonafide territorial control, the faucets were turned on.