ABC weapons represents the untraditional weapons of the 20th century:
The acronym ABC was deemed fit when large numbers of troops and civilians were to be educated on these new weapons, and how to protect against them, in the mid-20th century. The term was found to be less advantageous after the post-1968 radicalization, when the word Atomic seemingly was considered negatively charged after forceful left-wing campaigns against Atomic Power and the Atom Bomb.
See further: Weapons of mass destruction.