Some ideas I have come up with are:- bellum est infandum war is an abomination inmite est bellum war is pitiless res cruenta et infanda est Mars War is a blood-soaked atrocity Mars furit infandus War blasphemously rages out of control. Marte nulla pestis saevior est no instrument of destruction is more savage than war.
For 'infandus' I suppose 'nefandus' could be substituted, the difference apparently being that nefandus implies the idea of a crime which nefandus does not necessarily always do, as 'arma nefanda' = "war so base that it is not to be spoken of without horror'. 'Caesar' In De Bello Hispaniensi writes of the barbarians 'nefandum crudelissimumque facinus aunt adgressi'.