The Most Outdated Teaching of Jesus

Do you think Christians should go to war? On the one hand, Jesus said ‘Love your enemies’ and 'Turn the other cheek’, but he also said, “The one without a sword should sell his garment and buy one.” How do we reconcile the two teachings without being guilty of twisting the Bible? Did Jesus really change the Old Testament teaching about “an eye for an eye and a tooth for a tooth”?