&gt;  the 30 Years&#x27; War, The Crusades, the Sudanese War, etc... - would indicate that at least some number of the participants are involved purely because they think Heaven&#x2F;Jannah&#x2F;something else awaits and a god is being pleased.<p>I haven&#x27;t studied all of those wars, but my understanding has been that behind every religious explanation for war is a political power struggle.<p>Religion is used to get ordinary people to go to war, certainly.  If it wasn&#x27;t religion, it would be something else that speaks to people&#x27;s emotions and desire to belong to a group.  (Patriotism, &#x27;Duty&#x27;, &#x27;Honor&#x27;, etc.)<p>For two of your examples:<p>The crusades cemented the power of the Papacy and Holy Roman Empire in Europe, partly by sending a lot of armed powerful people to fight elsewhere.  It also was an attempt to reunite Catholicism under the Roman Pope (i.e. it was a massive land&#x2F;tax&#x2F;power grab by the Pope at the time).  Fighting other faiths occurred, and was certainly used as a reason for people to leave their homes and travel hundreds of miles to fight foreigners.  (I&#x27;m pretty convinced very few people do that willingly.)<p>The whole Protestant reformation taking off at all (Luther was not the first person to rail against the perceived hypocrisies of the Catholic church) and subsequent 30 years war was generally driven by a desire of the various princes and kings involved to remove themselves from Catholicism.  The 30 years war also quickly devolved past Protestants vs. Catholics and largely into various factions jostling for power.