p president obama weighed whether to make good on an earlier threat. a red line for us is we start seeing a bunch of chemical weapons moving around or being utilized. reporter: at the time trump tweeted repeatedly opposing action, to our very foolish leader, he said, do not attack syria. if you do many very bad things will happen, and from that fight the u.s. gets nothing. there is no upside and tremendous down side. and he told cnn why do we care? let isis and syria fight, and let russia they re in syria already. let them fight isis. reporter: then thursday and about face. it is in this vital nation at security interest of the united states to prevent and deter the spread and use of deadly chemical weapons. reporter: and trump s decision to strike syria was a unilateral one, after once chasening president obama for considering a go-it-alone
attack syria. if you do, many very bad things will happen and from that fight the u.s. gets nothing. there is no up side and tremendous down side. and he told cnn let isis and syria fight. let are ush srussia fight isis. reporter: then thursday an about-face. it is in the national security interests of the united states to prevent and deter the spread and use of deadly chemical weapons. reporter: and trump s decision to strike syria was a unilateral one after once saying don t go to alone approach. the president must get congressional approval. big mistake if he does not. president obama was ultimately unable to and scrapped plans to strike syria until 2014 when
u.s. gets nothing. there is no upside and tremendous downside. and he told cnn. we can t let isis and syria fight and let russia, they re in syria already, let them fight isis? reporter: then thursday and about face. it is in this vital national security interest of the united states to prevent and deter the threat and use of deadly chemical weapons. reporter: and trump s decision to strike syrias a a unilateral one after chasing obama for a go it alone approach. the president must get congressional approval before attacking syria. a big mistake if he does not, trump tweeted in 2013, president obama was ultimately unable to and scrapped plans to strike until 2014 when arab countries also participated in military action. well perhaps this is also
this as sort of a prelude to what we re doing in north korea. if we put our chips on the table with the t-lams, let s use diplomacy in a powerful and assertive way to shape this problem and rem solve it without more destruction. thank you all very much tonight. next, more breaking nutsz at this moment. the possibility of a major white house shake you have. this is breaking at this moment. we ll get you the very lightest on what we re laerg on that as our reporters break this. also coming up later this hour, we will talk about the same president trump who launched a major strike against syria who once said this why can t we let isis and syria fight and let russia they re in syria already let them fight isis? now and at&t, get the ultimate in entertainment plus unlimited data. get directv now for $10 a month when you have the new at&t unlimited plus plan.
reporter: this is also a startling about face for president trump. he repeatedly argued against military action in syria. why can t we let isis and syria fight and let russia, they re in syria already, let them fight isis? reporter: tweeting repeatedly after the last chemical weapons attack four years ago, that the u.s. should stay out of the conflict and suggesting that president obama needed congressional action before taking action. a step that donald trump did not take last night. the white house did inform two dozen lawmakers before taking action. legislators on both sides of the aisle are urging the president to involve congress if the administration decides to do more. the president stated concern with the humanitarian situation on the ground in syria also starkly different from his campaign rhetoric. if i win, they re going back. reporter: in which he argued against allowing syrian refugee into the united states. i always say trojan horse.