After nearly 16 years of military and diplomatic efforts, the U.S. cannot secure Afghanistan from the Taliban. During that time, the administrations of George W. Bush, Barack Obama and Donald Trump all wanted to believe that if they could just find the right U.S. troop levels and fine-tune the assistance provided to the government of Afghanistan, things would work out. But it never happened. Victory remains elusive.

Now, as the American public and its elected leaders grow impatient with the unending war and realize that doing more of the same will never produce different results, out-of-the-box proposals are on the table. As is often the case, frustration is making things that once appeared infeasible suddenly seem appealing. One such proposal is the idea of replacing some or even most U.S. troops in Afghanistan with private security contractors. ...