Hello local warlord. We're the Christians and we'll loan you some muscle and weapons to defeat your enemies, if you'll convert to our Universal Religion and require your subjects to convert. Once you win, we'll crown you and give you God's stamp of approval as King. Just let us put the crown on your head and you can do as you please. If you need anyone dead, just come to us and we'll find them guilty of a heresy, and give God's stamp of approval to their death sentence. Oh, and our Symbol is a crucifix, which is this awesome tool of torture and death that will totally keep your population in compliance with Your laws.

Their need for Symbolism will be their downfall.