- A threshold which may not be crossed without severe consequences.
- A threshold which must be met to avoid severe consequences.
- A line in the sand.
- A line which must not be crossed.
- A line which no one should cross.
- A line which when crossed demands action.
- Point of no return.
- No-go zone.
- Don’t go there.
- A non-negotiable demand
Downsides of red lines
The primary downside of a red line is the loss of flexibility.
A red line also raises the sociopolitical anxiety level based on an expectation or possibility of the consequences of the red line being crossed.
A red line is very bad advertising, informing the adversary that behavior anywhere up to but just short of the red line is okay, enabling and even encouraging bad behavior in the safe zone short of the red line. This gives adversaries a target or button to push to cause the country to experience heightened anxiety. It also suggests to the whole world that the adversary is much more important than they might actually be.
Another important downside of red lines is the high risk of loss of credibility should the red line be crossed without incurring the promised severe consequences in a very prompt manner.
Finally, the declaration of a red line may offend or challenge the adversary to such an extent that they are emboldened to continue the undesired behavior and maybe even take it a step further just to overcome the perceived insult
Tool of last resort
A red line should be considered only as a last resort, after all other viable alternatives have been exhausted.