In 2013, President Barack Obama went to Congress to ask for an authorization of force against Syrian President Bashar al-Assad -- and he was turned down, in large part thanks to opposition from Republicans in Congress.
Here are the biggest Republican flip-flops in Syria that have happened over the last four years.
1.) President Donald Trump. Trump is, of course, the most notable person to change his mind on the merits of attacking Syria. In 2012 and 2013, he regularly attacked Obama for his desire to get involved with the Syrian conflict, and even suggested at one point that Obama would go to war with Syria to boost his flagging poll numbers.
2. Rep. Paul Ryan (R-WI). Although Ryan gave Trump his approval for Thursday night's airstrikes, in 2013 he said that Obama's proposed military strike "cannot achieve its stated objectives" and could make things worse.
3. Rep. Jason Chaffetz (R-UT). On Thursday evening, Chaffetz sent out a tweet that read, "God bless the USA!" But in 2013, he said he would oppose the use of force in Syria on the grounds that he saw "no clear and present danger" to the United States that would justify using force.
4. Rep. Marsha Blackburn (R-TN). Blackburn announced in 2013 that she would oppose Obama's Syrian airstrike after being briefed. On Thursday evening, she approvingly re-tweeted President Trump's quote that "no child of God should ever suffer such horror."
5. Sen. Marco Rubio (R-FL). Although Rubio has been blanketing the airwaves praising Trump's airstrikes, in 2013 he said that "I have long argued forcefully for engagement in empowering the Syrian people, I have never supported the use of U.S. military force in the conflict."
6. Sen. Orrin Hatch (R-UT). Hatch gave Trump's actions an "amen" on Twitter Thursday evening, but in 2013 he said that he had "strong reservations about authorizing the use of force against Syria."
7. Rep. Pete Olson (R-TX). Olson cited his experience as a Navy veteran as a reason for opposing the use of force against Syria in 2013. Now, however, he is cheering on Trump by praising the president for doing what Obama would not.
8. Rep. Robert Aderholt (R-AL). The congressman on Thursday night gushed about Trump's airstrike, but in 2013 he worried that Obama had not done enough to seek a "diplomatic" solution to the crisis.
9. Rep. Larry Bucshon (R-IN). In 2013, the congressman opposed intervention in Syria on the grounds that he hadn't met a single person in his district "who believes we should fire missiles into Syria."
10. Sen. Cory Gardner (R-CO). In 2013, Gardner expressed "skepticism" of striking Syria and argued that he didn't see "a compelling and vital" national interest in such an attack. On Thursday evening, he called Trump's strike against Syria a "long-overdue action."
