"Russia vows to shoot down any and all missiles fired at Syria. Get ready Russia, because they will be coming, nice and new and 'smart!' You shouldn't be partners with a Gas Killing Animal who kills his people and enjoys it!"

Trump was responding to a warning by Russia that she would shoot down U.S. missiles fired at her Syrian allies, and she reserved the right to fire on U.S. warships and bases from which any such missiles were launched.

The "Gas Killing Animal" was Syrian President Bashar Assad.

That afternoon, Defense Secretary James Mattis dialed it down. Had he seen enough evidence to convict Assad of a poison gas attack in Douma, Mattis was asked. His reply: "We are still assessing the intelligence. … We're still working on this."

Thursday morning, Trump seemed to walk back his threat: "Never said when an attack on Syria would take place. Could be very soon or not so soon at all!"