sentences:  He has also made a case for intervening in nature to alleviate the suffering of wild animals when doing so would not cause more harm than good.McMahan's main contributions to just war theory are made in his book "Killing in War" (OUP, 2009), which argues against foundational elements of the traditional theory of the just war theory.Against Michael Walzer, he claims that those who fight an unjust war can never meet the requirements of "jus in bello".