This week added the specter that another capricious decree may be in the works, when the Russian military reported that President Vladimir Putin and Trump had reached a private agreement at their Helsinki summit to join forces to rebuild war-torn Syria. Such a deal would mark a major change for the U.S. troops battling the Islamic State, who are barred by law from cooperating with Russian troops fighting on behalf of the Syrian regime…

Before Trump, “you certainly never had a directive coming straight from the president via Twitter,” said a former senior defense official who spoke on condition of anonymity to discuss military officials he knows. “That adds an extra layer of instability and stress to an organization that is already under a lot of stress.”

Loren Schulman, who served in the Pentagon and on the National Security Council under presidents George W. Bush and Barack Obama, said past administrations had “a policy process where you don’t spring really big changes on the Pentagon with no warning at all.”