In most cases, obviously, soldiers fought because a government drafted them and gave them a rifle. At every point too, we see the role of nationalistic sentiment, commercial rivalries, and simple greed. But can we ever separate out such motives from the religious? Was that not also true of the medieval crusades?

Religion appears in so many contexts in WW1. Religion shaped the national identities and ambitions of several of the key players, especially Germany and Russia, both of which defined themselves as messianic nations. In both countries too, secular elites delved deeply into apocalyptic and prophetic ideas, giving their nations a millenarian bent.

Famine, plague, death and war... that's a pretty good description of 1917-18. The war was meant to end quickly, but by 1917 it seemed to be set until the end of time. No wonder everyone dreamed of an apocalyptic intervention.

Just because many modern academics are very secular does not mean that we should ignore those factors in earlier generations - and by that, I don't just mean five or six centuries ago.

Apocalyptic expectations ran riot in 1917, and had a major influence on Allied policies towards Palestine and the Jewish people. The propaganda of all nations was amazingly religious and apocalyptic - ghosts and visions, crucifixions and sacrifice, crusaders and holy warriors.

Much to my surprise, the Islamic scriptures in the Quran were actually far less bloody and less violent than those in the Bible.

When the war started, religion and superstition (whatever the difference is) permeated the lives of ordinary soldiers, who lived in a thought world not too far removed from the seventeenth century.