According to CND, who originated the Peace Symbol, it is a superposition
of the international semaphore code positions for N (nuclear) and D (disarmament),
inscribed in a circle:

   N        D

   o       |o
  /+\      \+\
 O | O      ||
  / \      / O

Well, that's the best I can draw them. The D is supposed to be straight up and down
for the most part, but I'm sure you get the point.