Summary:
Before
In 2013, after it was widely reported that the President of Syria used chemical weapons on civilians in Syria, then President Obama declare that the US would take military action. Trump at time came out strongly against this action in a series of tweets stating Obama should avoid going into Syria despite the chemical attacks. He also stated that if Obama was to strike Syria, he must seek authorization from Congress.
What will we get for bombing Syria besides more debt and a possible long term conflict? Obama needs Congressional approval.
— Donald J. Trump (@realDonaldTrump) August 29, 2013
The President must get Congressional approval before attacking Syria-big mistake if he does not!
— Donald J. Trump (@realDonaldTrump) August 30, 2013
After
On April 6th, 2017, just a few days after the President of Syrian once against used chemical weapons on his people, Trump ordered military strikes on Syria without receiving Congressional authorization or even notifying Congress ahead of the attacks.