Back in the day, venereal disease was the bane of the bored and horny soldier, and military propaganda posters resorted to sensationalist tactics to make privates scared of their privates. Mother Jones has collected some of these stunningly bizarre placards.
The idea of stern military men preventing their troops from consorting with dubious orifices may be titter-worthy, but VDs could debilitate armies. Says Mother Jones:
Army medical records dating back to the Revolutionary War show significant soldier losses due to venereal diseases. In a two-year period during the Civil War, the Union Army documented 100,000 cases of gonorrhea. During World War I, the Army lost 7 million person-days and discharged more than 10,000 men because they were ailing from STDs. Once Penicillin kicked in in the mid-1940s, such infections were treatable. But as a matter of national security, the military started distributing condoms and aggressively marketing prophylactics to the troops in the early 20th century
You can find more of these at Mother Jones' website. The article also links to another collection of anti-VD army posters. One anecdote notes that Stan Lee cut his teeth illustrating anti-VD propaganda posters in the Korean War. Sexcelsior!
Designed and reproduced by 912th Engineer Air Force Headquarters Co., Orlando, Florida
The American Social Hygiene Association
Cyril Jones, 4th Medical Corps Division, Australia.
Staff Sgt. Peterson, Goodfellow Field Venereal Disease Control Series 2, No. 1
c. 1940, National Library of Medicine, History of Medicine Collection
H. Dewitt Welsh [via here]