The particle curtain was a technological advancement made by Human scientist Hanson Smith in the mid 21st century. The particle curtain created a tactical advantage in the balance of power among Earth's nation-states, whicht led to the nuclear exchange at the end of the Third World War. (TOS novel: Prime Directive)

Certain details of the Eugenics Wars and the Third World War as related in this novel do not appear to be consistent with canonical information later established.