The United States fired cruise missiles on Friday at a Syrian airbase from which it said a deadly chemical weapons attack had been launched this week, the first direct US assault on the government of Bashar al-Assad in six years of civil war.
US President Donald Trump ordered the step his predecessor Barack Obama never took: directly targeting Assad's military with air strikes in punishment for the chemical weapons attack, which killed at least 70 people, many of them children.
That catapulted the United States into a confrontation with Russia, which has military advisers on the ground assisting its close ally Assad.
"Years of previous attempts at changing Assad's behaviour have all failed and failed very dramatically," Trump said as he announced the attack from his Florida resort, Mar-a-Lago, where he was meeting Chinese President Xi Jinping.
"Even beautiful babies were cruelly murdered in this very barbaric attack," he said of Tuesday's chemical weapons strike, which Western countries blame on Assad's forces. "No child of God should ever suffer such horror."
The times we are living in call for difficult decisions - Proud of my father for refusing to accept these horrendous crimes against humanity https://t.co/yV0oJuC9dE— Ivanka Trump (@IvankaTrump) April 7, 2017
The swift action is likely to be interpreted as a signal to Russia, and also to other countries such as North Korea, China and Iran where Trump has faced foreign policy tests early in his presidency.
The Syrian army said the US attack killed six people at its air base near the city of Homs. It called the attack "blatant aggression" and said it made the United States a "partner" of "terrorist groups" including Islamic State. Homs Governor Talal Barazi told Reuters the death toll was seven.
A spokesman for Russian President Vladimir Putin said the strike had seriously damaged ties between Washington and Moscow. Putin, a staunch ally of Assad, regarded the US action as "aggression against a sovereign nation" on a "made-up pretext", spokesman Dmitry Peskov said.
Russian television showed craters and rubble at the site of the airbase and said nine aircraft had been destroyed.
ATTACK SAID TO BE "ONE-OFF"
US officials said they had taken pains to ensure Russian troops were not killed, warning Russian forces in advance and avoiding striking parts of the base where Russians were present.
Western allies of the United States spoke out in support of the decision to launch the strikes. Several countries said they were notified in advance, but none had been asked to take part.
US officials and allies described the attack as a one-off that would not lead to further escalation. It signaled Trump's determination to take "decisive action", US officials said.
For years, Washington has backed rebel groups fighting against Assad in a complex multi-sided civil war under way since 2011 that has killed more than 400,000 people. The war has driven half of Syrians from their homes, creating the world's worst refugee crisis.
The United States has been conducting air strikes against Islamic State militants who control territory in eastern and northern Syria, and a small number of US troops are on the ground assisting anti-Islamic State militias. But until now, Washington has avoided direct confrontation with Assad.
Russia, meanwhile, joined the war on Assad's behalf in 2015, action that decisively turned the momentum of the conflict in the Syrian government's favour.
His decision to strike Syrian government forces is a particularly notable shift for Trump, who in the past had repeatedly said he wanted better relations with Moscow, including to co-operate with Russia to fight Islamic State.
However, Trump had also criticised Obama for setting a "red line" threatening force against Assad if he used chemical weapons, only to pull back from ordering air strikes in 2013 when Assad agreed to give up his chemical arsenal.
Trump said this week's chemical attack "crosses many, many lines", an allusion to Obama's threat that was not carried out.
Russian media long portrayed Trump as a figure who would promote closer relations with Moscow. At home, Trump's opponents have accused him of being too supportive of Putin.
US spy agencies say Moscow intervened with computer hacking to help Trump beat Hillary Clinton in last year's election, and the FBI is investigating whether Trump campaign figures colluded with Moscow, which the White House denies.
TRUMP BLAMED ASSAD
Trump ordered the strikes a day after he blamed Assad for this week's chemical attack in the Syrian town of Khan Sheikhoun.
The Syrian government and Moscow have denied that Syrian forces were behind the attack, but Western countries have dismissed their explanation - that chemicals were released in an air strike on a rebel weapons depot, as beyond credibility.
Video of the aftermath of Tuesday's chemical attack was shown around the world this week, depicting the limp bodies of small children choking while rescue workers hosed them down to try to wash off the poison gas. In Russia, state television blamed rebels and did not show footage of victims.
Tomahawk missiles were launched from the USS Porter and USS Ross around 0040 GMT on Friday, striking multiple targets - including the airstrip, aircraft and fuel stations - on the Shayrat Air Base, which the Pentagon says was used to store chemical weapons.
The attack was a "one-off," a US defence official told Reuters, meaning it was expected to be a single strike with no current plans for escalation.
US Secretary of State Rex Tillerson said the strike did not mean the wider US policy on Syria had changed.
"This clearly indicates the president is willing to take decisive action when called for," he told reporters. "I would not in any way attempt to extrapolate that to a change in our policy or our posture relative to our military activities in Syria today. There has been no change in that status."
IRAN DENOUNCES STRIKE
Iran, which backs Assad, denounced the US strike, saying it was "dangerous, destructive and violation of international laws" to use chemical weapons as an excuse for unilateral action.
Israel, where right-wing Prime Minister Benjamin Netanyahu is a supporter of Trump, welcomed it: "In both word and action, President Trump sent a strong and clear message today that the use and spread of chemical weapons will not be tolerated," Netanyahu's office said in a statement.
Over the previous few months, many Western countries had been quietly backing away from long-standing demands that Assad leave power, accepting that rebels no longer had the power to remove him by force. But after the chemical weapons attack on Tuesday, several European countries said Assad must go.
"President Assad alone is responsible for this development," the German government said in a statement after the French and German leaders spoke by phone on Friday morning.
The attacks spurred a flight to safety in global financial markets, sending yields on safe-haven US Treasury securities to their lowest since November. Stocks weakened in Asia and US equity index futures slid, indicating Wall Street would open lower on Friday. Prices for oil and gold both rose, and the dollar slipped against the Japanese yen.