Could it be that IIslamists had Saint Bernard as teacher?
To Die or to Kill for Christ Is Not Criminal, but Glorious
About the lawfulness of war against the pagans, Saint Bernard, the Mellifluous Doctor, has these glowing words:
But in truth the knights of Christ fight the battles of their Lord with all tranquillity of conscience, fearing neither sin by the death of their enemies nor the danger of their own death, because death inflicted or suffered for Christ’s sake bears no trace of crime and often brings the merit of glory. In the former case, there is a gain for Christ; in the latter, Christ is gained, Who doubtless both willingly accepts the death of an enemy for punishment and more willingly offers Himself to the soldier for consolation. The knight of Christ, I say, kills with tranquil conscience and dies even more tranquilly. In dying he benefits himself, in killing he benefits Christ. For he bears not a sword without cause; he is the minister of God for the punishment of evil and the exaltation of good. When he kills a malefactor, it is not homicide but, so to say, “malecide”; and he is clearly considered the avenger of Christ in the case of those who do evil, and the defender of Christians. Moreover, when he himself is killed, it is understood that he has not perished, but that he has arrived in eternal glory. The death, therefore, that he inflicts is again for Christ; the death that he receives is his own gain. The Christian glories in the death of a pagan, because Christ is glorified; in the death of a Christian, the liberality of the king is revealed, because the soldier is taken away to be rewarded. Furthermore, the just man will rejoice over the one when he has seen the punishment. Concerning the other, a man will say: “If indeed there be fruit to the just: there is indeed a God that judgeth them on the earth” (Ps. 57:12). Not that the pagans should be slain if by any other means they can be impeded from persecuting and oppressing the faithful. But presently it is better that they be killed so that, in this way, the just men do not bend to the iniquity of their hands, for on the contrary, certainly the sinners’ rod will be upon the lot of the just.
Saint Bernard, the Mellifluous Doctor
De laude novae militiae, in Migne, Patrologia Latina, vol. 182, col. 924.
Crusade for a Christian Civilization.