May, who has regained confidence after winning support for her tough stance on Syria and Russian Federation, will make a statement to parliament on her decision to join the and France in Saturday's strikes in retaliation for a suspected gas attack.
"We are confident in our own assessment that the Syrian regime was highly likely responsible for this attack and that its persistent pattern of behaviour meant that it was highly likely to continue using chemical weapons", she said.
British medical and scientific experts analyzed reports, images and video footage from the incident and concluded the victims were exposed to a toxic chemical, she said.
Ms May said a "significant body of information", including intelligence, pointed to the Syrian government's responsibility for the chemical weapons attack, which killed up to 75 people. "And I will make them", May, 61, said of the intervention.
Much of the criticism will come from opposition lawmakers, but the prime minister may also have to work hard to defend her speed of action to members of her own Conservative Party who had wanted parliament recalled.
In her post-strikes speech, Theresa May made a reference to the poisoning of former Russian spy Sergei Skripal and his daughter in Britain, saying that the military action in Syria "will also send a clear signal to anyone else who believes they can use chemical weapons with impunity".
Britain joined its American and French allies on Saturday, 14 April as the Royal Air Force jets hit targets in Syria, in response to an alleged chemical attack in Douma.
It was justified to "alleviate humanitarian suffering", and that argument had been "used by governments of both parties in the past".
Corbyn won approval for a debate on parliament's rights in regard to British military action on Tuesday, and parliament debated long into the evening on Monday on the government's strategy in Syria, particularly regarding civilians there.
Pointing to some of the evidence known to the OPCW council, Wilson said: "The OPCW has recorded more than 390 allegations of chemical weapons use in Syria since the fact-finding mission was established in 2014".
"She authorized military action with no mandate", said one Conservative lawmaker on condition of anonymity.
Ahmet Uzumcu, the director-general of the Organization for the Prohibition of Chemical Weapons, told a meeting of the group's executive council in the Hague on Monday that his team has not yet deployed to Douma two days after arriving in Syria.
"She could have recalled parliament last week", the veteran peace campaigner said on Sunday.
USA and United Kingdom officials briefing reporters said the attacks could be used for espionage or intellectual property theft or for laying the groundwork for destructive attacks should tensions escalate.