Pablo and Anselmo represent two radically separate poles in the book, reflecting two different ways to approach the reality of war. Anselmo believes killing is always wrong, but must be done if the war is to be won. It should never be done with any pleasure, though, if one is to pass as a moral human being. Pablo's a big fan of brutal killing: he is in Pilar's story (he tells her he enjoyed "all" of the massacre of the fascist civilians), and he is at the end of the book. Anselmo's loyal, and will follow orders to the end. He doesn't like war, but will fight in order to end it. Pablo enjoys being able to kill in war, but doesn't like the risks it entails. It seems he's willing to do anything to serve himself and his precious ponies.