President Donald Trump announced Friday night that he ordered the U.S. military to conduct precision missile strikes against the Syrian government, in retaliation for a chemical attack executed against its citizens.
The order — carried out in conjunction with French and British allies — marked a dramatic reversal for Trump. As recently as last week, had been saying that he wanted the U.S. to withdraw its forces from Syria. Then, days after a suspected chemical attack by Syrian forces on rebels, Trump warned over Twitter that missile strikes would be coming.
In a speech from the White House, Trump declared that the U.S.-led coalition's intent was to "establish a strong deterrent against the production, spread, and use of chemical weapons. Establishing this deterrent is a vital national security interest of the United States."
Although Trump has indicated his unwillingness to stay in Syria long-term, the president added that "we are prepared to sustain this response until the Syrian regime stops its use of prohibited chemical agents."
During Friday's speech, Trump noted that the strike was underway, but did not give further details of the targets or the military assets used. There were initial indications the strikes could occur over days, but officials at a Pentagon briefing later Friday said that the current wave of attacks was over.
Defense Secretary James Mattis, in a later briefing from the Pentagon, said Trump ordered the strikes to destroy Syria's chemical weapons development infrastructure.
There were reports of Syrian air defense forces firing back, but no immediate indications that U.S. planes were struck.
Trump used the address to also directly call out Russia and Iran, which back the regime of Syrian President Bashar Assad.
"To Iran and to Russia, I ask: What kind of a nation wants to be associated with the mass murder of innocent men, women and children?" Trump said. "Hopefully someday we will get along with Russia, and maybe even Iran. But maybe not."
Russia responded over Twitter, with a statement from its ambassador to the U.S., Anatoly Antonov.
"We warned that such actions will not be left without consequences," the statement said. "All responsibility for them rests with Washington, London and Paris."
The Syria assault generated mixed reviews on Capitol Hill. Sen. Tim Kaine, D-Va., denounced the attack. "We need to stop giving presidents a blank check to wage war," he tweeted. "Today it's Syria, but what's going to stop him from bombing Iran or North Korea next?"
Separately, House Minority Leader Nancy Pelosi demanded Trump seek Congressional authorization, as well as a clear strategy for an endgame.
On the other hand, Sen. John McCain, R-Ariz., lauded the strikes, but called for Trump to draw up a more comprehensive plan for the region.
"Airstrikes disconnected from a broader strategy may be necessary, but they alone will not achieve U.S. objectives in the Middle East," McCain said in a statement. Earlier this week, McCain, the Senate Armed Forces Committee chairman, said Trump's talk of withdrawing from Syria had emboldened Assad to launch the alleged chemical attack.
The U.K. emphasized that the strikes were specifically targeted against Syria's purported chemical-weapons program.
"Our action is proportionate, specifically aimed at degrading the regime's ability to use chemical weapons and deterring further such appalling acts," said a statement from Britain's Royal Air Force. "It is therefore focused on regime facilities linked to the production and use of chemical weapons."
British Prime Minister Theresa May also issued a statement about the strikes.
"This is not about intervening in a civil war. It is not about regime change. It is about a limited and targeted strike that does not further escalate tensions in the region and that does everything possible to prevent civilian casualties," she said in a statement.
"And while this action is specifically about deterring the Syrian Regime, it will also send a clear signal to anyone else who believes they can use chemical weapons with impunity," May added.
For the last six days, Trump has sharpened his rhetoric against Syria and its most powerful ally Russia and issued a threat via Twitter of a potential U.S. strike against the war-torn country.
"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 said.
The tweet came on the heels of an alleged chemical weapons attack believed to be carried out by forces aligned with the Assad regime in Douma, a town that was held by Syrian rebels.
The Assad regime has denied responsibility for the April 7 attack and has since repositioned a significant amount of air assets to Russian-controlled airfields in hopes that Washington would be reluctant to strike there.
A source, who spoke on the condition of anonymity, told CNBC the U.S. was considering striking eight potential targets. Those targets include two Syrian airfields, a research center and a chemical weapons facility.
The source also noted that a Russian Navy ship was stalking the U.S. Navy guided-missile destroyer, the USS Donald Cook, which is the closest U.S. Navy vessel in the region.
Last year, the Trump administration lobbed a total of 59 Tomahawk cruise missiles from the Navy destroyers U.S.S. Porter and U.S.S. Ross in the eastern Mediterranean.
The missiles hit aircraft hangars, ammunition bunkers, air defense systems and radar. Additionally, the Pentagon said Russian forces in Syria were formally notified before the strike, but Moscow was not involved in the military operation.
Syria began developing chemical weapons in the 1970s, with significant help from the Soviet Union. And while the Syrian government only admitted to its chemical weapons program in 2012, its foreign ministry claimed that the stockpile was only for deterrence.
The Syrian government denies ever using chemical weapons during its now seven-year civil war, and says it got rid of all its chemical weapons in 2013. That is the same year it ratified the 1997 Chemical Weapons Convention that banned the production, storage, and use of chemical weapons.
CNBC's Mike Calia contributed to this article.