Keep it under your hat! Careless talk costs lives" 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
A pure visual pun on a common idiom. The 'hat' in 'keep it under your hat' is literally a soldier's helmet, instantly targeting the military audience and tying a casual phrase to war.
Steal this when
When you can use a visual pun on a well-known phrase to instantly communicate both the action and the context.