Why only partial? And why now in the waning days of his presidency? After all, when Trump campaigned in 2016. his expressed aim was to bring all the troops home from those two countries. He repeatedly vowed to bring an end to America's "forever wars."

There is a simple explanation for Trump's failure, one that unfortunately so many Americans are loathe to consider: It's not the president who is in charge of foreign policy. Instead it is the Pentagon and the CIA that are in charge.

Trump had four years to bring home those troops. Clearly he wanted to. The reason he didn't — the reason he still can't — is because the Joint Chiefs of Staff and the CIA won't let him.