The U.S. military — together with French and British forces — struck three targets inside Syria on Friday night, just days after Bashar Assad’s government allegedly carried out a chemical attack on a Damascus suburb and amid new U.S.-Russia tensions.

In a televised address, President Donald Trump announced that strikes against Assad’s forces were “now underway.”

“This massacre was a significant escalation in a pattern of chemical weapons use by that very terrible regime,” Trump said.

An hour later, Gen. Joseph F. Dunford Jr., chairman of the Joint Chiefs of Staff, said the strikes had ended, but Defense Secretary James Mattis warned Assad that there would be retaliation for future chemical attacks.

“Right now, this is a one-time shot and I believe it has sent a very strong message to dissuade him, to deter him from doing that again,” Mattis said.

The targets were all associated with the Assad regime’s chemical weapons program, including a scientific research center around Damascus.

Trump ordered his second round of U.S. strikes on the conflict-stricken country over a week after he called the apparent Syrian government attack that killed nearly 50 people, including women and children, “barbaric.”

The retaliatory act appeared imminent, but then was delayed for several days as U.S. officials debated Trump’s options and deliberated with French and British leaders. 

As Trump and other officials weighed their options, American and Russian warships traversed the Mediterranean Sea all week, with Moscow sailing its Syria-based fleet of 11 warships. U.S. combat aircraft moved around the region. And both countries still have sizable numbers of military boots operating on Syrian soil. Tensions boiled this week between the Cold War rivals at their hottest temperatures since the 1980s, with experts warning the Syrian situation could spiral out of control.

Some lawmakers, including Virginia Democratic Sen. Tim Kaine, urged the White House to seek congressional authorization before launching the strikes.

Kaine, a member of the Senate Foreign Relations and Armed Services committees who has been pushing for a new war authorization to replace the open-ended 2001 authorization, called the strikes illegal.

“Assad must face consequences for his war crimes, but Presidents cannot initiate military action when there isn’t an imminent threat to American lives,” Kaine said in a news release Friday night.

But others, like Senate Foreign Relations Chairman Bob Corker, R-Tenn., told reporters a one-off strike or even one lasting just a few days would be within any commander in chief’s legal authorities under the U.S. Constitution.

Last spring, Trump ordered 59 Tomahawk cruise missiles be fired at a list of Assad military targets; experts concluded, however, they had little effect and did not alter Assad’s behavior or decision-making.

The strikes comes less than a week into the tenure of Trump’s new national security adviser, John Bolton. Just what role Bolton played in Trump’s decision to strike is unclear.

The president’s order to strike came amid a whirlwind of other matters on his mind. That list included a Monday FBI raid on the office of his personal attorney, Michael Cohen; new reports that he has multiple times been close to firing special counsel Robert S. Mueller III, who is leading the Russia investigation; the release of former FBI Director James B. Comey’s book that paints a scathing picture of him; and speculation he soon will fire Deputy Attorney General Rod Rosenstein to find another Justice official who will curb or fire Mueller.

As he considered his Syrian attack plan, Trump lashed out at Comey on Friday morning after book excerpts leaked. He called the former FBI chief an “unthruthful slime ball,” among other insults.

Trump’s focus

Trump’s public fuming about those issues left Kaine and fellow Democrat Mazie K. Hirono of Hawaii, also a Senate Armed Services member, concerned about his ability to focus on a military operation. Trump has “shown very little ability to focus on anything much else” just as his administration is planning possible military action in Syria, Hirono told Roll Call.

The entire situation in the troubled Middle Eastern country has left Republican and Democratic lawmakers urging Trump and his team to fashion a long-term Syria strategy.

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Sen. Jeanne Shaheen, D-N.H., issued a statement Monday noting she supported U.S. military action in 2013 and the administration’s strikes last year. But the Senate Armed Services and Foreign Relations member added that “military efforts alone are not sufficient to adequately deal with the Syrian civil war.”

Watch: Lawmakers Press Pompeo On Syria Response Without Congressional Approval

Like other Democrats, Shaheen is pressing the White House for a long-term plan. Many Republicans in recent days have echoed senior Senate Armed Services member Roger Wicker, R-Miss., who told CNN on Monday that “we need to make Bashar al-Assad pay a price.”

Late Monday morning, things seemed to be moving quickly: Trump told reporters he planned to act fast, first saying a decision could come in the next 48 hours. The situation intensified on Wednesday morning when the president responded to a warning by Russian officials that they intended to shoot down any U.S. missiles fired at Syrian government targets.

“Get ready Russia, because they will be coming, nice and new and ‘smart!’” the commander in chief tweeted, a departure from a vow he has long expressed to not telegraph his military actions. (The latter was an apparent reference to technology installed in American weapons to make them more precise.)

Russia vows to shoot down any and all missiles fired at Syria. 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!

— Donald J. Trump (@realDonaldTrump) April 11, 2018

Trump was responding to a threat from Alexander Zasypkin, the Kremlin’s ambassador to Lebanon.

“If there is a strike by the Americans, then … the missiles will be downed and even the sources from which the missiles were fired,” Zasypkin told Hezbollah’s al-Manar TV on Tuesday night, according to Reuters. He was referring to U.S. cruise missiles and the Navy ships from which they would be fired, like the 59 Tomahawk missiles that Trump ordered fired at Syrian government targets after a chemical attack last spring.

Russia did not intercept any of those missiles, though experts and lawmakers say that attack did little to change Assad’s behavior.

But by Wednesday afternoon, Defense Secretary James Mattis and White House Press Secretary Sarah Huckabee Sanders signaled that planning was still ongoing. The next day, even Trump himself made clear his administration — along with France and Great Britain — was not moving as quickly as his Monday tweet implied.

‘Game of chicken’

Security and foreign policy experts said Wednesday it is virtually impossible to know how the U.S. operation might play out — largely because predicting Russian President Vladimir Putin’s reaction and any subsequent retaliation to that by Trump could go many different ways.

“The biggest danger is we accidentally kill some Russians,” said Stephen Biddle of the Council on Foreign Relations and George Washington University. “If Russia then responds and Trump doesn’t back down, this could spiral out of control — and quickly.”

“What we are seeing is a classic game of chicken — except both sides have nuclear weapons,” he added. 

A major question is whether the new round of U.S. strikes will change Assad’s calculus — and that of his Russian and Iranian backers, said Daniel Davis, a retired Army officer who served in Iraq and Afghanistan.

“Are we just going to spank Assad then move on?” said Davis, now with the Defense Priorities think tank. “Firing missiles into Syria is not helping the Syrian people. To truly change the situation there, the U.S. would need to take out Assad’s storage facilities, helicopters, artillery, and anything else he needs for more chemical attacks. It’s ludicrous to think Russia would sit back and allow that to happen.”

“Nothing is off the table,” Trump said Monday when asked specifically about the possibility he would order a second round of U.S. military strikes in the conflict-torn country in a year. Experts have concluded that the first round last year had little effect and did not alter Assad’s behavior or decision-making.

“We cannot allow atrocities like that,” Trump said during a Cabinet meeting with his top national security officials seated around him. “It was atrocious. It was horrible. This is about humanity and it can’t be allowed to happen.”

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The strikes marked a stunning about-face by Trump in just a few days — again. This time, the president, who repeatedly last week expressed his desire to withdraw all American forces from Syria and let other parties find a solution to that country’s years-long conflict, found out a chief executive’s whim can quickly be overcome by tragic events.

Operation déjà vu?

Trump was moved to act a year ago by images of children killed by that Assad government chemical attack, and he expressed similar sentiments Monday.

“As bad as the news is around the world,” he told reporters, “you just don’t see those images.”

The president went off-script on March 29 during a speech in Ohio, telling a friendly audience: “We’re knocking the hell out of ISIS. We’ll be coming out of Syria, like, very soon. Let the other people take care of it now.”

On April 3, he first repeated the withdrawal pledge before saying he would be talking with key U.S. allies in the region like Saudi Arabia before making a final decision. But he qualified his statement about diplomacy by again making his stance clear: “As far as Syria is concerned, our primary mission, in terms of that, was getting rid of ISIS. We’ve almost completed that task.”

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The White House issued a statement the next day signaling the president would not follow through on his threat.

“The United States and our partners remain committed to eliminating the small ISIS presence in Syria that our forces have not already eradicated,” the White House said in a statement that did not, as many do, have Trump’s or Sanders’ name attached. “We will continue to consult with our allies and friends regarding future plans.”

Friday’s strikes came less than a week after Trump’s new national security adviser, John Bolton, started his new job. Just what role he played in Friday night’s decision to strike is unclear.

In February, Bolton chided the international community for doing, in his view, too little to change Assad’s behavior; but in 2013, he said the United States should stay out of the conflict there because intervening would not be in Washington’s strategic interests.