How to justify a belief in god

I was listening to someone on the radio talk about how being in war and having to order people to engage in combat matures one very quickly. It occurred to me that this issue could explain how religion became so widespread with humanity so early on with our societies.

I am sure it must be a very difficult process to order someone to go to a war zone and engage in a fight that could result in their death. How do you rationalize that order? It could help if you believe that the person who died is going to some heavenly reward. It can also help in explaining to the person why they should obey the order to engage in an activity that may kill them.

A belief in a supernatural afterlife makes it easier for the commander to give these orders. But how do you make the solders believe? You now have to start creating an entire belief system to support the assertion that this supernatural afterlife actually exists. One person cannot do this, so they find people willing to help. This develops the clergy, who quickly recognises the financial and social benefits of being in charge of this activity. The commander states his ideas come from this god and therefore, are not to be questioned.

It is harder to convince adults of a new idea, so they start with the young children. After hundreds and thousands of years, the ideas become entrenched in the society. Entire families are raised with this supernatural concept. Believers are rewarded, the skeptics are killed or run off.  The other leaders in other societies around this group embrace this idea because they also need people willing to follow their orders without question that will fight to the death.

You now have a self sustaining belief system in place. The people commanding the deaths have also been raised from birth to believe the lie. The people being killed have been raised from birth to accept the lie. The clergy have been raised from birth to accept the fables as truth. And the story continues to be told and accepted because the children are told from their most trusted source, their parents, that the story is true.