The very fact that doctrine is hewn from bitter controversy and tested through time is sufficient reason to make them a focus of theology.
I was raised in an evangelical Methodist church. Evangelical meant that though you had been baptized and made a member of the church on Sunday morning, you still had to be 'saved' on Sunday night. I wanted to be saved, but I did not think you should fake it.
In the Crusades, getting the Holy Land back was the goal, and any means could be used to achieve it. World War II was a crusade. The firebombing of Tokyo by Doolittle and the carpet bombing in Germany, especially by the British, showed that.
One of the problems we currently have is there hasn't been in the population any serious engagement with the ethics of war because we have an all-volunteer army. I would think the return to the draft would be an intervention that would require discussion that might be more helpful in terms of our ability to limit war.