The Islamic Extremists have some kind of religious immunity. People largely respect religion and they also respect the religions of their enemies. It’s sort of like the immunity offered to the Red Cross.
One of the tactics of the Crusading Armies was to build hospitals in enemy lands. The hospitals would be immune from attack so the invading forces stayed inside the hospitals. The invading armies were protected from the locals by the alleged neutrality of the hospitals. The crusading knights fought the Muslims to a standoff that survived until the Ayatollah Kholmeini conquered Iran and re-started the old fued.
Can one religion conquer another? No, not historcally but neither can a nation or a nation-state. So far no nation has attempted to declare war against christianity or against Islam but the combination of a religious based nation – such as the Islamic Republic of Iran and a religion – like Islam, would be a powerful enemy. So far the world has not devised a solution so the war rages on.
There’s a hospital on Rhodes established by the Knights. It’s no longer a military base but there are we saw canonballs in the courtyard durin our visit there in 2002. It’s not even a working hospital and it would be futile to use it as a foreword staging area but a large group of people who would defend a hospital in Iran might resurrect the Hospitallers, the crusading Knights who conquered the Holy Lands in the thirteenth century. History repeating itself because some lessons are not easily learned.