Millions volunteered or were drafted for military duty during World War II. The majority of these citizen-soldiers had no idea how to conduct themselves to prevent inadvertent disclosure of important information to the enemy. To remedy this, the  US government established rules of conduct. The following is excerpted from a document given to each soldier as he entered the battle area.

WRITING HOMETHINK! Where does the enemy get his information — information that can put you, and has put your comrades, adrift on an open sea: information that has lost battles and can lose more, unless you personally, vigilantly, perform your duty in SAFEGUARDING MILITARY INFORMATION?

THERE ARE TEN PROHIBITED SUBJECTS

1. Don’t write military information of Army units — their location, strength,, materiel, or equipment.

2. Don’t write of military installations.

3. Don’t write of transportation facilities.

4. Don’t write of convoys, their routes, ports (including ports…