The Order of Things

I remember this coming up a lot in my research again, I'm reaching back over 10 years. Some people said that the only reason why Christians had a problem with military service was because it was idolatry. In our time, we flip the order. We see the objection to killing as the primary prescription against joining armies. But there's an order to these things. So first is under who is your Lord? Secondly, what does your Lord demand? And third, therefore, why do you participate or refuse to participate in the practices demanded by your Lord in the system in which you find himself?