Love thy neighbor

When Aquinas addressed the issue of war and whether it was a sin or not. I was surprised he did not mention Romans 11:19-21 (Do not take revenge, my dear friends, but leave room for God’s wrath, for it is written: “It is mine to avenge; I will repay,” says the Lord. On the contrary: “If your enemy is hungry, feed him; if he is thirsty, give him something to drink. In doing this, you will heap burning coals on his head.” Do not be overcome by evil, but overcome evil with good. (‭Romans‬ ‭12‬:‭19-21‬ NIV)).  According to that scripture we should show love to our neighbor by tending to his or her needs and looking past the pains he or she has caused up, and in doing that we will be overcoming evil with good. Now, I am not sure if a country or government could actually survive and flourish without war. If it could that would be amazing; however, I felt as if these verses would have helped back up Aquinas's argument that war was sin. It would have fit perfectly with the argument that out enemies are our neighbors and we should treat our neighbors as we would want to be treated  which is objection three under "Whether it is lawful to lay ambush in war?"

P.S. I commented on Caleb's.