It was the chemical weapons attack that so nearly led to direct war between the US, the UK, France and the Syrian government; a war which most likely would have delivered the whole of Syria to IS and Al-Qaeda extremists.
It seems like every we look up there is another incident of domestic terrorism, and specifically, to use the language that President Obama has been perplexingly wary of using, radical Islamist terrorism. From the Boston Marathon Bombing in 2013, to the more recent shooting in San Bernardino, the "lone wolf attack" feels like the new American reality.