Do U.S. Strikes Send a ‘Message’ to Rivals? There’s No Evidence

In the Trump administration’s telling, its missile strike on a Syrian airfield and its dropping of the so-called mother of all bombs over Afghanistan were more than military missions.

They were a signal of American resolve, and of President Trump’s willingness to use force, that would deter adversaries worldwide. ...

The notion that military action in one part of the world will deter adversaries in all others, long common in stump speeches and on cable news chatter, has at times profoundly influenced American foreign policy.

There is only one problem: Repeated investigation has found that this notion is baseless.

Jonathan Mercer, a University of Washington political scientist who studies so-called signaling in foreign policy, said this line of reasoning “drives me crazy.”

His entire field of study, he added, had never found evidence that would support the administration’s claims. ...