The US has launched between fifty and sixty cruise missiles, each carrying a 1,000 pound warhead, at Ash Sha'irat air base in Syria. The base is thought to have been the origin of the recent chemical attack.
The missiles were timed to all hit within seconds of each other to provide a maximum effect.
In order to avoid incidents involving aircraft carrying bombs the cruise missiles were launched from two US warships based in the Mediterranean.
Russia has warned the US of 'negative consequences.'