What did Donald Trump do today?

He got very, very angry at the staff resigning in protest over his Syria capitulation.

Trump was already supposed to be in Mar-a-Lago for a 16-day retreat, but the third government shutdown of the year meant that optics required him to stay in Washington. He claimed to be spending it working, posing for photos of fake bill signings with blank paper and capped pens. But since he is not taking part in any discussions around his refusal to sign a spending bill without support for his "wall," he was left to his own devices for much of the day.

The inevitable result was a Twitter tirade, aimed mostly at the two senior military and diplomatic figures who have resigned in protest over his sudden decision to abandon U.S. allies in Syria: Defense Secretary James Mattis, and Brett McGurk, the Special Presidential Envoy for the Global Coalition to Counter ISIL.

Trump specifically claimed not to know who McGurk was, and called him a "grandstander." It's not impossible that Trump genuinely doesn't know who his top diplomatic envoy is to a huge international coalition—or that he has forgotten. But there's another reason Trump might have wanted to pretend not to know McGurk: to conceal the fact that an abrupt withdrawal from Syria greatly benefits Turkey.

Turkey fears an independent Kurdish region on its border with northern Syria, and has repeatedly demanded that McGurk be fired for his "pro-Kurdish" stance. (Syrian Kurds are the United States' main allies in the anti-ISIS effort in Syria.) Turkey has all but declared that with the U.S. out of the region, it will launch an attack on the Syrian Kurds. This abandonment of American allies is what prompted both Mattis's and McGurk's resignations.

Previously, Trump had largely ignored Turkey's hostility towards the YPG, but the U.S.-Turkey relationship has changed. The Trump administration is not only abandoning its Kurdish allies to Turkish attack, but has recently been receptive to the Turkish government's demands that the United States surrender a political enemy of the current president who currently lives in Pennsylvania.

Turkey now has increased influence over Trump because he will not—or cannot—cut political ties with the de facto power in Saudi Arabia's government, Crown Prince Mohammed bin Salman. When bin Salman ordered a clumsy assassination on Turkish soil of the Washington Post columnist Jamal Khashoggi, a critic of the Saudi regime, the Turkish government gained diplomatic leverage from its ability to expose bin Salman's responsibility. Trump, who has personal and family financial ties to the Saudi elite, was forced to sue for peace on the Saudi government's behalf.

In short, by attacking McGurk on his way out the door, Trump is likely trying to draw attention away from the question of whether he is entirely in control of his own Syria policy.

Why does this matter?

• Senior military and diplomatic staff don't quit their jobs for no reason.

• A president who isn't fully free of foreign influence where American national security is concerned is not fit for office.