Here's what we know so far, and what the United States, Russia, Syria and the UK have been saying about the first direct US assault against Mr Assad's forces since civil war broke out six years ago.
- Two American Navy destroyers in the Mediterranean fired 59 Tomahawk missiles at Al Shayrat airfield in Western Syria
- The strikes were launched in response to a Syrian government air strike on a rebel-held town near the city of Idlib, where over 80 people reportedly died and hundreds more suffered symptoms consistent with reaction to a nerve agent, such as sarin
- A Pentagon spokesperson claimed the strikes targeted "aircraft, hardened aircraft shelters, petroleum and logistical storage, ammunition supply bunkers, air defense systems, and radars." No chemical weapons are believed to have been destroyed
- The Syrian army are reporting six deaths at the airbase, while the Pentagon say Syrian-allied Russian forces were informed of the strikes via the so-called "deconfliction line" used to prevent clashes
- Some reports suggest the airbase was largely evacuated before the strikes took place
What did Donald Trump say?
- Announcing the strike last night, Mr Trump said: "It is in this vital national security interest of the United States to prevent and deter the spread and use of deadly chemical weapons"
- Speaking at his Mar-a-Lago resort, the President added: “Previous attempts at changing Assad’s behaviour have failed and failed very badly. Tonight, I’m calling all civilised nations to help us end the slaughter and bloodshed”
- He reportedly opted for the less severe of two military options presented to him by advisors
How did Russia respond?
- Russia has called for a UN security council meeting to discuss the strikes, and reportedly suspended its agreement with the US to avoid clashes in Syrian airspace
- Kremlin spokesperson Dmitry Peskov said President Vladimir Putin considers the strikes an "act of aggression" made on a "made-up pretext"
- He said the strikes would "inflict major damage on US-Russia ties", and suggested they were intended as a distraction from mass civilian deaths allegedly caused by US bombing in Iraq
- Kremlin announces Russia has suspended the agreement that prevents direct conflict with American forces, a memorandum designed to prevent incidents and ensure flight safety
How did the United Kingdom respond?
- 10 Downing Street describes the attack as an "appropriate response to the barbaric chemical weapons attack launched by the Syrian regime", and said the UK "fully supports" the intervention
- A poll conducted by Sky News released on Thursday found that 51 per cent of the British public would support British military involvement alongside other Western countries in Syria, while 32 per cent would oppose it
How has Syria reacted?
- The SAA Command view the attack as a "blatant act of aggression", which makes the USA a "partner" of terror organisations such as Isis and al-Qaeda linked coalition Haya Tahrir Sham, currently at war with the Syrian government
- Members of rebel and Islamist groups have celebrated the attacks through their social media channels, with spokespeople expressing hopes Mr Trump will escalate American interventions
How has the world responded?
- The USA's main allies in NATO and elsewhere largely fell into line, with France, Germany, Australia, Israel, Turkey, Saudi Arabia, New Zealand and Japan all backing the strikes
- Allies including the UK, France and Germany were informed of the assault on the air base beforehand, but not given a chance to discuss the move
- Iran, which also has fighters on the ground backing Assad's forces, condemned the assault
- China, which has vetoed previous UN resolutions against Assad, said they condemned both "the use of chemical weapons" and "the use of force", in a guarded reference to the air strikes. Indonesia took a similar line
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