phrase
Red Line
A publicly declared limit that, if crossed, will provoke a serious response.
Origin
The phrase has 19th-century origins but became diplomatic vocabulary in the 20th century โ most notoriously when President Obama said the use of chemical weapons in Syria would be a 'red line' in 2012, then declined to enforce it militarily when Assad crossed it. The episode made 'red line' synonymous with the question 'will you actually do anything?'.
Modern usage
Used in geopolitics, negotiation, and personal relationships. A red line announced and not enforced is worse than no red line at all.
Tags
diplomacy
threat
credibility