Seems like the present jihadists do not even follow the rules in the Qur'an:


"People who want to remain neutral in war should be left alone and not be troubled in any way. As in Qur'an:
Or those who approach you such that they neither have the courage to fight you nor their own people [and are such that] had Allah willed, indeed He would have given them power over you, and they would have fought you. So if they withdraw from you, and fight not against you, and offer you peace, then Allah does not give you permission to take any action against them. 4:90
People who neither take part in a battle nor are able to take part in it – as per the dictates of custom as well as sense and reason – should not be killed. As according to a hadith:
'Abdullah Ibn 'Umar (rta) reports from the Prophet (sws) that once in a battle when it became known that a woman had been killed, the Prophet (sws) emphatically forbade the killing of the women and children.[18]

Ibn Athir further adds:[23]

Wrong no one and exercise no torture.
Do not touch the children, women and the old.
Do not destroy fruit-trees and fertile lands.
Do not kill sheep and cattle.
Respect all religious persons who live in hermitages or convents and spare their edifices.


Objectives of warfare
According to verses 2:190-194, the Qur'an implies two objectives:[10]

Uproot fitnah (in Arabic: ÝÊäÉ) or persecution (forcing people to renounce their religion)
Establish supremecy of Islam in the Arabian peninsula "