THERE ARE TEN PROHIBITED SUBJECTS
1. Don’t write military information of Army units — their location, strength,, material, 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 of embarkation and disembarkation), time en route, naval protection, or war incidents occurring en route.
5. Don’t disclose movements of ships, naval or merchant, troops, or aircraft.
6. Don’t mention plans and forecasts or orders for future operations, whether known or just your guess.
7. Don’t write about the effect of enemy operations.
8. Don’t tell of any casualty until released by proper authority (The Adjutant General) and then only by using the full name of the casualty.
9. Don’t attempt to formulate or use a code system, cipher, or shorthand, or any other means to conceal the true meaning of your letter.
10. Don’t give your location in any way except as authorized by proper authority. Be sure nothing you write about discloses a more specific location than the one authorized.
SILENCE MEANS SECURITY — If violation of protective measures is serious within written communications it is disastrous in conversations. Protect your conversation, emails and letters and be even more careful.
If you come home during war your lips must remain sealed and your written hand must be guided by self-imposed censorship.