Red line (phrase)
The red line, or "to cross the red line", is a phrase used worldwide to mean a figurative point of no return or line in the sand, or "the fastest, farthest, or highest point or degree considered safe." == Origins == The origin of the phrase in English traces back to the "Red Line Agreement" in 1928 between the largest oil companies of Great Britain, the US, and France at the time of the end of the Ottoman Empire. At the time of signature, the former empire's borders were unclear.