President Donald J. Trump’s decision to respond to the chemical weapons attack in Syria with a bombardment of 59 Tomahawk missiles was the most presidential thing he has done so far. He’s not the first president to use an air strike as a form of gesture politics and, sadly, he won’t be the last.

But it had to be done. It’s what a President Hillary Clinton would’ve done. It’s what President Barack Obama should’ve done. What does it accomplish? Maybe nothing. But you cannot let chemical weapons go unnoticed. This year marks the centennial of the United States’ entry into World War I, the Great War, in which millions were gassed. The response was “Never again.” And yet it has happened, again and again. ...