What did Donald Trump do today?

He gave a speech outlining a new Afghanistan policy, apparently--though not necessarily--the one he told the military he would.

Trump's address tonight on the US military involvement in Afghanistan was a major reversal from one of the few consistently held foreign policy views he had articulated during and before his campaign. Candidate and private citizen Trump repeatedly denounced President Obama for wasting American "blood and treasure" and urged him to withdraw immediately. But an abrupt withdrawal from Afghanistan would now cost Trump political capital he doesn't have--and would happen over the strenuous objections of actual military experts.

Previously, Trump had dealt with this awkward contradiction by all but abandoning Afghanistan policy to the military. He allowed the Pentagon unprecedented authority to determine troop levels for itself, and took himself out of the decision-making process for greenlighting major operations. 

Trump offered no advance text of his announcement, which is unusual--and also kept the military and Pentagon in the dark as well. The military leaders who developed Trump's were reportedly concerned that Trump would announce a substantially different policy, either impulsively or deliberately.

So what?

• It's bad if the United States military can't trust that what a president says on Friday will still be policy on Monday.