President Trump is reportedly considering a change of leadership at the Pentagon, perhaps after the midterm elections. He shouldn’t do it. Rather than ask Defense Secretary Jim Mattis to resign, Mr. Trump should keep him through 2020.
To be sure, I am exactly the kind of moderate foreign-policy establishmentarian who would say such a thing. That people like me admire Mr. Mattis is one of the reasons Mr. Trump may want a change. Yet there are two compelling reasons to keep “Chaos,” Mr. Mattis’s call sign and preferred nickname,...