What we know to be FACTS:

On 4 April 2017, the town of Khan Shaykhun in Syria's Idlib province, was struck by a heavy airstrike followed by massive civilian chemical (sarin nerve gas) poisoning, including children.

At the time of the attack the town was under the control of Tahrir al-Sham, formerly known as the al-Nusra Front — a Sunni Islamist terrorist organization fighting against Syrian Government forces in the Syrian Civil War, with the aim of establishing an Islamist state in the country.

President Donald Trump, the U.S. Pentagon, and the UK (in the person of Foreign Secretary Boris Johnson) blamed the attack on the forces of Syrian President Bashar Assad. The Russian and Syrian governments said it was caused by the Syrian Air Force's destruction of a nearby rebel-operated chemical weapons warehouse.