Note
In the pages of QST, the phrase "civil defense" is first seen in 1942 but doesn't seem to gain a lot of traction until after WWII and the beginning of the Cold War. Initially called "civilian defense," and later "civil defense."
For example:
QST, Feb 1942, p. 7
QST, Oct 1950, p. 10.
QST, Feb 1951, p. 11.
QST, Feb 1951, back cover. (or an addendum to the back cover)
QST, Apr 1951, p. 81.
And advertisers quickly pick up the phrase for marketing.