Intellectual developments since the mid-1960s have served to assist the efforts of those responsible for American policy in the Vietnam war subsequently to empty the history of that conflict of ethical critique. This article argues for the necessity of ethically informed historical enquiry and, with respect to Vietnam, proposes that there now exists the best opportunity for a generation for scholars to construct a fresh and credible moral history of the war. Increasingly, we have access to the perspectives of the ‘other side/s’: the revolution in the south, the Democratic Republic of Vietnam regime in Hanoi, the People's Republic of China, and the USSR. An examination of the motivations and interactions of these parties, combined with the continuing exegesis of American policy debates, makes clear just how critical concerns (and failures) of ethics were to the development of the conflict. In particular, it clarifies the manner in which US leaders abdicated responsibility in exaggerating the relatively limited strategic challenge that they faced in south-east Asia. Vietnam was not a ‘necessary war’; nor can the decision to fight it – given its predictable consequences for south Vietnamese civilians and American soldiers alike – simply be explained away through the discourse of the honest ‘mistake’.