If You Must Talk . . . Tell it to the Marines" poster
The pattern
This still is filed under Negative headline.
Define
The first line is a warning, a refusal, or a negated claim. Something the reader cannot skim as praise.
Mechanism
Pattern interrupt. A negative is harder to slide past than a compliment. The payload must arrive immediately after the stop.
Verdict
The category is full of sunny claims
Why it works
Re-appropriates a common idiom into a literal directive about operational security. The bold, crude brushstrokes give it a raw, urgent feel.
Steal this when
You can twist a well-known phrase to serve a completely new, urgent message.