The US strikes a Syrian air base, firing its first salvo against the government in the six-year-old civil war.
The missile attack is being seen as a message to Damascus, deterring it from repeating Tuesday's horrors in Idlib, which saw at least 80 people killed.
The US intervention may come as a shot in the arm for the Syrian opposition, reeling under a government offensive backed by Russia in recent months.
Moscow's response has been swift, calling the US move an act of "aggression".
Allies rallied around to support Trump, for whom the strike could be a masterstroke in deflecting the growing criticism at home.
So, will this response to the suspected Idlib chemical attack have a decisive impact on the unending violence? And how will Trump's 180-degree turnaround affect US-Russia relations?
Presenter: Nick Clark
Guests:
Pavel Felgenhauer - columnist for the Novaya Gazetta
Haid Haid - Syria specialist at Chatham House
Kurt Volker - former US ambassador to NATO
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