The US, Britain and France have launched a series of military strikes in Syria – ending days of speculation and anxiety as to how the the West would respond to Bashar Al-Assad’s alleged use of chemical weapons against civilians.

While Syria and their Russian allies had denied chemical weapons were deployed a week ago in the Damascus suburb of Douma, the three Western nations claimed they had proof they had been used against civilians and had no alternative but to act.

Syrian television reported that Syria’s air defences, which are substantial, responded to the attack. After the attack ceased and the early morning skies went dark once more, vehicles with loudspeakers roamed the streets of Damascus blaring nationalist songs.

US President Donald Trump delivered a televised address in which he said the US was prepared to sustain pressure on Mr Assad.

“The evil and the despicable attack left mothers and fathers, infants and children, thrashing in pain and gasping for air. These are not the actions of a man; they are crimes of a monster instead,” Mr Trump said.

British Prime Minister Theresa May said the West had tried “every possible” diplomatic means to stop Assad from using chemical weapons. “But our efforts have been repeatedly thwarted” by Syria and Russia, she said.

Theresa May says Syrian air strikes are in Britain's national interest

“So there is no practicable alternative to the use of force to degrade and deter the use of chemical weapons by the Syrian regime,” Ms May said. “This is not about intervening in a civil war. It is not about regime change.”

French President Emmanuel Macron said in a statement that a target of the strike was the Syrian government’s “clandestine chemical arsenal”.

The Associated Press said Mr Trump did not provide details on the joint US-British-French attack, but it was expected to have included barrages of cruise missiles launched from outside Syrian airspace. He described the main aim as establishing “a strong deterrent” against chemical weapons use. The Syrian government has repeatedly denied any use of banned weapons.

The decision to strike, after days of deliberations, marked Mr Trump’s second order to attack Syria. He authorised a barrage of Tomahawk cruise missiles to hit a single Syrian airfield in April 2017 in retaliation for Mr Assad’s aleged use of sarin gas against civilians.

At the Pentagon, Secretary of Defence Jim Mattis said the strike was “harder” on the Syrian regime than the 2017 strike and targeted “Syrian chemical weapons infrastructure”. He described it as a “one-time shot”. adding: “I believe it has sent a very strong message.“

Mr Mattis said there were “no reports of losses” on the part of US and allied forces participating in the strike, which included manned aircraft. Mr Mattis estimated the air campaign was about twice the size of the 2017 strike. He added that the US expected the Syrian government and its allies to conduct a “significant disinformation campaign”.

The strikes that hit early on Saturday in Syria came hours before inspectors from the Organisation for the Prohibition of Chemical Weapons were set to arrive to inspect the site of the apparent attack.

Gen Joseph Dunford, the chairman of the Joint Chiefs of Staff, said the US did not coordinate targets with or notify the Russian government of the strikes, beyond normal airspace “de-confliction” communications.

In his speech, broadcast at 9pm on the US east coast, Mr Trump said: “To Iran and Russia, I ask, what kind of nation wants to be associated with the mass murder of innocent men, women, and children? The nations of the world will be judged by the friends they keep.”

Mr Trump publicly confronted the countries that have been on the side of Mr Assad’s regime. Russia has repeatedly blocked measures regarding Syria in the United Nations Security Council as well. Mr Trump said Russia must decide whether it wants to ”continue down this dark path or join with civilised nations” in combating the use of chemical weapons and ending the ongoing conflict.

The two countries have repeatedly exchanged barbs at the UN the last week over setting up an investigation mechanism regarding the latest suspected attack. Russia has argued specifically over what US Ambassador to the UN Nikki Haley has called an “attribution” mechanism, an investigation to figure out which party actually carried out the supposed chemical weapons attack.

Russian Ambassador to the UN Vasily Nebenzya had turned the focus to the “bellicose rhetoric” of the US and Mr Trump’s hint at a possible missile strike akin to what took place last April after a chemical attack in the town of Khan Sheikhoun, adding that “not only the use of force, the threat of force, flies in the face of the UN charter”. He spared no words of caution to US allies as well, saying: “There are those with tacit consent that are...possibly becoming complicit in a possible military misadventure”.

Emmanual Macron says France has prood the Assad used chemical weapons in Syria

Experts have noted this strike will have more impact than the strike in response to Khan Sheikhoun, where 86 civilians were reported dead in April 2017. The US, just three months into Mr Trump’s presidency, had launched 59 Tomahawk missiles to strike the to strike Shayrat air base, where US intelligence pointed to as the source of the chemical weapons attack. However, unlike that missile strike, the “precision strike” in response to the Douma attack, which killed 60 people and injured 1,000, will not take place on just one night, but multiple.

For its part, Russia has repeatedly denied that the Assad regime, what it calls the “legal government of Syria,” has anything to do with the attack in Douma and that there is “no trace” of chemical weapons use. Mr Nebenzya said earlier today at the UN that neither the residents of Douma nor Russian investigators found evidence of an attack and had “weighty justification to believe, we have even information to believe, that what took place is a provocation of participation of certain countries intelligence services”. Ms Haley retorted that Russia simply wants to protect Mr Assad.