People forget that the popularity of being
anti-war is relatively new, like maybe 100-150 years old. World War 1 popped off so quickly specifically because moral objections to war from the standpoint of "violence is wrong" were just not even part of the discussion. Even during World War 2, most objections within the US to entering the war were based on it just not being our problem.
Up until the last century, violence was seen as just another necessary part of living, and morality only came into play when it involved you're own community.