LONDON — The leaders of France and Britain used phrases such as “red line” and “horrific suffering” on Saturday to defend their decisions to join the U.S.-led strike against Syria for its suspected chemical attack.

France and Britain stressed that their military response was limited, successful and not designed to topple the regime of President Bashar al-Assad. The goal at home, meanwhile, was to soften the political fallout amid questions and clamor about taking part in the military action led by President Trump.

The moves by British Prime Minister Theresa May and French President Emmanuel Macron are unlikely to pose direct threats to the stability of their governments. But the reaction to the allies’ coordinated attacks in Syria is playing out differently in Europe than in the United States.

In Britain, it was an open question: How much did the public support May’s decision to bomb Syrian targets? Many Britons are still upset about then-Prime Minister Tony Blair’s decision to join President George W. Bush in the Iraq War, claiming that the country was misled and that the results were disastrous.

In France, Macron has a similar uphill climb to win over a public highly cautious about getting too involved in another crisis in the Middle East as the memory of a Libyan operation in 2011 still looms large. French forces, along with NATO allies, helped topple the regime of dictator Moammar Gaddafi but ultimately entered a conflict that dragged on for months longer than anticipated.

“We have seen harrowing images of men, women and children lying dead with foam in their mouths,” May said during a news conference at 10 Downing Street. Referring to the Syrian regime, she said: “We are also clear about who was responsible for this atrocity.”

U.S. coalition strikes Syria with cruise missiles

The guided-missile cruiser USS Monterey fires a Tomahawk land-attack missile at Syria as part of an allied strike. President Trump ordered a joint force strike on Syria with Britain and France in response to a recent suspected chemical attack by Syrian President Bashar al-Assad. (U.S. Navy)

Yet her opponents pounced — sensing a deep skepticism in Britain about whether military action was the right course, or a feeling that May did not go about it in the preferred way. 

Jeremy Corbyn, the leader of the opposition Labour Party, has said that Britain should not be “taking instructions from Washington and putting British military personnel in harm’s way.”

“Bombs won’t save lives or bring about peace,” he said in a post on his Facebook page. “This legally questionable action risks escalating further.”

Vince Cable, the leader of the Liberal Democrats, didn’t rule out supporting military action if a case were made but said that May was wrong not to seek parliamentary consent. 

“Riding the coattails of an erratic U.S. president is no substitute for a mandate from the House of Commons,” he said.

Nicola Sturgeon, the first minister of Scotland, tweeted: “Air strikes have not resolved situation in Syria so far — nothing I’ve heard persuades me they will do so now.”

She added: “UK foreign policy should be set by Parliament, not US President.”

May is not required by law to win approval from lawmakers before committing Britain to military action. But the convention in Britain is that lawmakers be given a chance to vote. Parliament is in recess until Monday, but she could have called an emergency session. 

When asked why she didn’t seek Parliament’s consent, May suggested that speed was essential. “For operational security reasons, it was right that we acted the way we did,” she said.

It is unclear how such a vote in Parliament would have turned out. The Iraq War casts a long shadow over politics in Britain, and some lawmakers are wary about the effectiveness of military action on its own.

In 2013, David Cameron, then the prime minister, lost a vote in Parliament that was designed to pave the way for airstrikes against the Assad regime. Two years later, he won a vote for Britain to join the U.S.-led bombing campaign that targeted the Islamic State in Syria.

In France, Macron faced a skeptical public, but one that was willing to give him some leeway.

“Because we don’t have an Iraq problem in France, people tend to trust the executive on this,” François Heisbourg, a security analyst and former presidential national security adviser, said in an interview. 

Macron, who has long considered the use of chemical weapons in Syria “a red line,” was clear to underscore what he presented as France’s moral obligation to intervene.

“We cannot tolerate the normalization of the employment of chemical weapons, which is an immediate danger to the Syrian people and to our collective security,” he said in a statement Saturday.

According to French defense officials, 12 French missiles were fired in total. British Defense Minister Gavin Williamson said four Royal Air Force Tornado GR4 jets took part in the strikes. He told BBC Radio that initial assessments suggested that it was “a highly successful mission.”

In the days leading up to the strikes, opinion polls suggested that the French public was skeptical about the prospect of an attack.

But former president François Hollande and Benoît Hamon, the Socialist presidential contender last year, came to Macron’s defense in the past week, urging an end to humanitarian abuse in Syria. 

The loudest opposition in France was ultimately confined to the political extremes, factions with little clout in Parliament.

“It’s a North American revenge adventure, an irresponsible escalation,” said Jean-Luc Mélenchon, the leader of the far-left France Unbowed party. “France deserves better than this role. It must be the force of international order and peace.” Marine Le Pen, the leader of the far-right National Front, said much the same.

Macron and Florence Parly, France’s defense minister, emphasized the limited scope of the strikes.

“The targets were chosen precisely: These are the sites themselves that permitted the massacre of Syrian women and children in defiance of all the norms of law, in defiance of all norms of humanity,” Parly said.

McAuley reported from Paris.