The thin khaki line keeps the fate of Belgium from your hearth and home. Get into khaki now!" poster
The pattern
This still is filed under Problem-agitate-solve.
Define
Name the problem, make the cost of leaving it felt, then present the way out as relief.
Mechanism
Tension then release. The offer is not an interruption. It is the only door once the cost of staying is clear.
Verdict
The problem is known but not yet urgent
Why it works
It uses fear and the protective instinct. By referencing a known tragedy ('the fate of Belgium') and threatening 'Your Hearth and Home', it creates intense urgency.
Steal this when
You need to motivate action by highlighting a severe, impending threat that only your solution can prevent.