During the Syrian Civil War US President Obama argued in a 2012 speech that a chemical attack in Syria would constitute crossing a "red line" and that this would trigger a US military intervention against the government of Syrian President Bashar al-Assad. After this speech, and prior to the chemical attacks in Ghouta, chemical weapons were suspected to have been used in at least four attacks in the country. On March 23, 2013, the Syrian government requested the UN to send inspectors in order to investigate an incident in the town of Khan al-Assal, where it said opposition forces had used chlorine-filled rockets. However, on April 25 US Secretary of Defense Chuck Hagel stated that US intelligence showed the Assad government was likely to have used chemical weapons, in this case sarin gas.