Critics swiftly accused Britain and France of playing loyal deputies to an unpredictable American leader, viewed by many in Europe with suspicion or outright scorn.
Some worried it could further antagonize Europe’s hulking neighbor Russia at an already tense time.
British Prime Minister Theresa May was decried for not seeking parliamentary approval for Saturday’s coordinated airstrikes.
French President Emmanuel Macron was accused of compromising the independence of a country that famously stayed out of former US President George W. Bush’s 2003 invasion of Iraq.
And worst of all for the West, Saturday’s “one-shot” military operation may not substantially change the course of the war in Syria, the Associated Press wrote.
Analysts say the move could cost both leaders domestically.
May claimed that there was “no other choice” but to act fast, without taking time to recall Parliament from its break. Lawmakers are already crying foul.
While May wasn’t legally required to seek lawmakers’ approval, opposition leaders have suggested she had a moral responsibility to do so.
The tainted legacy of former British Prime Minister Tony Blair’s rush to back President Bush in Iraq has overshadowed the debate.
“Theresa May should have sought parliamentary approval, not trailed after Donald Trump,” said opposition Labour Party leader Jeremy Corbyn. He warned that May could face a backlash in Parliament, calling the allies’ bombing “legally questionable” and saying it risked further escalating “an already devastating conflict.”
May’s Conservative Party lost its majority last June, and since then, her government has limped from crisis to crisis.
In France, Macron is facing the worst labor unrest of his presidency so far, with strikes that halted two-thirds of French trains Saturday and weeks more of walkouts to come.
Macron drew criticism Saturday from the far-left to the far-right.
National Front leader Marine Le Pen tweeted that the strikes expose France to “unpredictable and potentially dramatic consequences,” and criticized Macron for not taking an “independent” stance.
In nine days, Macron goes to Washington for the first state visit under Trump’s presidency and he is already being seen as the mercurial US president’s lapdog.
The French leader is fighting to distance himself from comparisons to the 2003 Iraq invasion, which was motivated by false suspicions that Saddam Hussein possessed weapons of mass destruction.