Modern knight or Murderers?

Is war ethical? Is killing ever accepted, are material things ever more valuable than life? I dont think that there is any ethics or morals in war. War is about getting what you want by force and its irrational to put lives in danger for material resources or even for a religion. I belive that God has made us all equal and that it is a sin to kill other human beings. The war on self defense is the kind of war that is almost universally admitted to be justifiable, and is condemned only by Christ. Another war that can be justified and maybe ethical is the war of principle this war is the one like the American Civil war that one of the sides is honestly trying to make good change for the progress of the people. The war on democracy i think it is not justified at all and that people can have different points of view, different governments if they want. War on religion i think is really unethical because religions are supposed to teach morals and virtues and why would two different types of religions fight? I think its hipocritical from both religions to fight and murder people and then say that it is a sin! Would God allow this? War is also really expensive to cost and it is not logical to lose so much money to kill people and feel powerful. In my opinion if war actually helps a society it can be considered ethical but it cant be ethical if its just to get resources or change a government.