Henderson Protect Them. Join Civil Defense 1951. Poster depicts a mother shielding her children from a bright flash, doubtless a reference to the atomic bomb. The A bomb was tested 23 times at the Bikini atoll between 1948 and 1958. Bomb fears were so prevalent that building bomb shelters in American backyards became a brisk business. Hard to find. 22×14 mint, conservation backed.