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.

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Cruise missiles as well as U.S., French and British manned aircraft targeted sites in and around Damascus and Homs. (The Washington Post)

“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.”

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. 

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.
A Tomahawk land-attack missile is fired at Syria from the USS Monterey.
Smoke rises as the USS Monterey fires a Tomahawk missile.
A Tomahawk missile is launched toward Syria.
Smoke trails a missile after being fired from the USS Monterey.
President Trump addresses the situation in Syria from the White House.
Television news reporters broadcast live from outside the White House after Trump addresses the nation on Syria.
Defense Secretary Jim Mattis, center, and Joint Chiefs of Staff Chairman Gen. Joseph F. Dunford Jr., right, brief reporters on the U.S. strike on Syria during a news conference at the Pentagon in Arlington.
Missiles streak across the sky over Damascus as the United States launches an attack on Syria.
Damascus skies erupt with surface to air missile fire as the U.S. launches an attack on Syria targeting different parts of the Syrian capital Damascus, Syria, early Saturday, April 14, 2018. Syria's capital has been rocked by loud explosions that lit up the sky with heavy smoke as U.S. President Donald Trump announced airstrikes in retaliation for the country's alleged use of chemical weapons. (AP Photo/Hassan Ammar)
In this image released by the U.S. Air Force, a 34th Expeditionary Bomb Squadron B-1B Lancer aircraft departs from Al Udeid Air Base in Qatar. Trump declared “Mission Accomplished!” after the missile assault on the Syrian regime and warned another attack could follow if Damascus were to unleash more chemical weapons.
This photo released by the official Syrian news agency, SANA, shows antiaircraft fire in the sky after U.S. airstrikes targeted Damascus. Syrian air defenses responded to the joint strikes by the United States, France and Britain.
Explosions light up the Damascus sky with antiaircraft fire.
Syrian air defenses strike back after airstrikes in Damascus.
Chief spokeswoman Dana W. White, left, and Marine Lt. Gen. Kenneth F. McKenzie Jr. participate in a news briefing at the Pentagon.
A Defense Department graphic appears next to reporters as they listen to White and McKenzie during a briefing at the Pentagon.
McKenzie speaks during a news briefing at the Pentagon about the strike on Syria.
The Maxar News Bureau released a DigitalGlobe satellite image of a facility in Syria that was struck by U.S. coalition operations.
During a press tour organized by the Syrian information ministry, a journalist films the wreckage of a building described as part of the scientific studies and research center compound in the Barzeh district, north of Damascus.
A Syrian soldier sprays water on the wreckage of a scientific studies and research center building during the press tour.
A Syrian soldier films the damage to the scientific studies and research center after the attack near Damascus.
Photo Gallery: President Trump announced that the United States conducted a military strike against the Syrian government in response to a suspected chemical attack in a Damascus suburb. Cruise missiles as well as U.S., French and British manned aircraft targeted sites in and around the Syrian capital.

“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.