On the Tripwire of a ‘Red Line,’ It’s Often Presidents Who Trip

When President Biden declared over the weekend that he was drawing a “red line” for Israel’s military action in Gaza, he appeared to be trying to raise the potential cost for Prime Minister Benjamin Netanyahu as their relationship plummets to new depths.

But he never said what would happen, exactly, if Mr. Netanyahu ignored him and continued Israel’s military operation by invading the southern city Rafah, a step that Mr. Biden has said — repeatedly — would be a major mistake. It is unclear whether he hesitated because he did not want to signal what response he might be preparing, or because he did not want to be criticized if he backed away from whatever action he is contemplating.

Or perhaps, given his long experience in the Senate and the White House, he remembered that drawing red lines turned out badly for Barack Obama when it came to Syria, and for George W. Bush when it came to North Korea and Iran. American allies in the Middle East were stunned by Mr. Obama’s reversal. Mr. Bush was later judged to have invaded a country that had no nuclear weapons — Iraq — while the North tested its first nuclear weapon on his watch.

Mr. Biden’s line-drawing was immediately dismissed — and matched — by Mr. Netanyahu, who shot back: “You know, I have a red line. You know what the red line is? That Oct. 7 doesn’t happen again.” The prime minister was referring, of course, to the Hamas attack that killed 1,200 people in Israel, left scores more as hostages and precipitated a war now in its sixth month.

Such talk of red lines is hardly new: Leaders of all stripes, from heads of democracies to vicious autocrats, often invoke the phrase to describe moves that another country should not even contemplate, because the consequences would be