War crimes constitute breaches of LOIAC giving rise to penal accountability of the individuals who perpetrated the proscribed acts. In the past, it was frequently asserted that every breach of LOIAC was a war crime, but – as pointed out already by H. Lauterpacht – ‘textbook writers and, occasionally, military manuals and official pronouncements have erred on the side of comprehensiveness’ in making ‘no attempt to distinguish between violations of the rules of warfare and war crimes’.2179 It is currently clear that only select violations of LOIAC are stigmatized as war crimes.2180 Some of these violations are regarded as ‘grave’ breaches (see infra 1066). But ‘[o]ther serious violations’ of LOIAC are listed as war crimes in Article 8(2)(b) of the Rome Statute (see infra 1067). Of course, by itself, the adjective ‘serious’ (or, for that matter, ‘grave’) does not provide a useful compass indicating the contours of war crimes.2181 War crimes must be defined in specie.