Would anybody happen to know how this would fit in with “turn thy cheek”?
I’m not a theologian, but here’s my take on it.
We are, at minimum, encouraged to “turn the other cheek” when an injustice is done to us. However, we are not obliged, nor is it charitable to turn someone else’s cheek so he/she can be hit, killed or oppressed.
The Crusades were not about the Christian combatants avenging personal affronts or reprisals. Arab armies had conquered Greek Christians and Levantines. The Arab rule grew weak and was more and more dominated by various Turkic groups from Central Asia. The rule of the latter was quite harsh, and not only on Christians, but on many Arabs Muslims as well. The initial Crusades were against the Seljuks, a ferocious Turkic tribe that really was oppressing Christians in the Middle East. It was thought, and probably rightly, that the Muslim world posed a threat to Christian Europe. After all, the Muslim Moors were barely defeated at Tours, in France, and had sacked Christian churches in Italy and Spain and hauled Christians off to be sold in the slave markets.
Ultimately, the Crusades failed, mainly because Turkic tribes kept coming out of Central Asia, and not only drove out the Crusaders, but essentially destroyed Arab civilization; something from which it has never really recovered.
It must be remembered that Spain had its own Crusades; which the Christians ultimately won after centuries of struggle. The remoteness of Spain from the Central Asians would have played a part in that.
The Byzantine Empire, of course, fell to the Ottoman Turks, who essentially stamped out Christianity in what is now Turkey. The Ottomans attempted to conquer all of Europe twice, and were narrowly turned back each time.
That’s not a failure to “turn the other cheek”. That’s defending the potential victims.