The 'just war' is not the only tradition that has thought deeply about the moral and ethical context of the use of organised violence. This chapter offers an account of some of the critical alternative approaches to the ethics of war. These are pacifism and strategic non-violence, realism, feminism and postcolonial theory. Each of the approaches reject a number of the underlying assumptions about politics and ethics found in the just war tradition suggesting that it cannot act as a meaningful arbiter of political and military ethics because it misconstrues the fundamental nature of both. The chapter also offers a case study of the effort to defend 'preventive war', military action to avert a future harm before it actually materialises, and the effort of liberal institutionalists to loosen the just war tradition's prohibition on such wars.