Amid the many questions surrounding last night's ISIS-claimed attack on the Manchester Arena, two give insight into the ideology behind it: Why was a concert venue the target, and why were innocent children and teenagers the main victims?

The relative ease of attacks against soft targets is part of it. No matter the security precautions, public gatherings are vulnerable. Jihadi ideologues associated with both al-Qaeda and ISIS have long encouraged attacks at public events. As a second order effect, the clamping down on individual freedoms in the name of security is touted as a form of victory for such groups.

ISIS has at times justified its attacks against civilians for their role in electing politicians who carrying out strikes on their so-called ‘caliphate,’ framing such deaths as collateral damage, something used by other jihadi ideologues in justification of violence. 

However, jihadi targets can be selected for symbolic resonance and ideological significance, as well as vulnerability. Attacks have been framed as being against the perceived decadence and un-Islamic practice of the West. ISIS’ official claim of responsibility for the November 2015 Paris attacks described the Bataclan concert venue, where 89 people were killed, as a den of “prostitution and vice.”

After the Paris attacks, Mark Rowley, head of counter-terrorism for the Metropolitan Police, warned, “In recent months we’ve seen [many] more plans to attack Western lifestyle, going from that narrow focus on police and military as symbols of the state to something much broader.”

Such a belief derives from a violent interpretation of the Salafi principle of al-Wala w’al-Bara – loyalty only to Islam and disavowal of the non-Islamic. Within this enmity towards all things perceived as anti-religious, music has a special resonance. In ISIS’ ‘caliphate,’ instrumental music is banned, with the only permitted music being the unaccompanied nasheeds (anthems), which accompany their propaganda.

The cult of celebrity has been presented as idolatry (shirk) by jihadis, who believe it entails worship of figures other than God. The concert-goers were described in ISIS' claim of responsibility as mushrikun – idolaters or polytheists. The same belief has resulted in the destruction of shrines, tombs, and ruins across the Middle East.