US President Donald Trump declared it was "mission accomplished" after the overnight bombing campaign in Syria.
And he thanked the UK and France "for their wisdom and the power of their fine military".
Britain launched cruise missiles as part of the co-ordinated military operation with the United States and France in response to the chemical weapons attack in Douma one week ago.
Mr Trump said the joint strikes against the Syrian regime were "perfectly executed".
He added: "Could not have had a better result. Mission Accomplished."
Theresa May insisted that joining the military campaign was the "right thing for us to do" in the wake of the "harrowing" assault on the Syrian rebel-held town.
The Prime Minister also warned Russia that the air strikes should act as a warning to Russia over its use of chemical weapons.