Comment: Let's never forgive or forget Assad's silent weapon killing indiscriminately
The little girl stares into the distance while her limbs convulse. She is foaming from the mouth, desperately trying to get air into her tiny lungs. It's a battle she probably won't win. The girl doesn't know why she is dying.
She can't form any words, but her constricted pupils speak of the agony and horror she is going through.
On April 7, more than 40 people were killed and hundreds more injured in a suspected chemical attack on the last remaining opposition stronghold of Douma, near Damascus.
At 7.45pm that evening, 500 patients - most of them women and children - were taken to medical facilities with symptoms of exposure to chemical agents. Videos of the aftermath gave an unsanitised view of what happens when a toxic cocktail of chlorine gas and sarin is dropped on civilians.
Chemical weapons mercilessly, indiscriminately fill the lungs of the infants, young, and old. When you watch children taking their last breaths, you understand why this is a red line, whether you are the president of the United States or a person watching the horror unfold on the evening news.
The international community speaks of "war crimes" and "crimes against humanity", but it is images like these which push those terms beyond the abstract and turn our heads and hearts towards Syria's tortured population.
It is the pictures of babies taking their last breaths which focus all our minds on how this slaughter can be brought to an end.
And there's no shortage of slaughter in Syria. With the 24-hour news cycle throwing images of war at us every hour - of starvation, of broken bodies pulled from the rubble of bombed-out hospitals and schools, of refugees taking their place in the graveyard of the Mediterranean Sea - we cannot allow ourselves to get desensitised to the suffering and killing of human beings. That in itself is a red line.
By giving the chemical weapons a special rank in Syria's blood orgy, we have to ensure we don't send the message that the massacre of civilians is acceptable as long as there is no poison gas.
In fact, most Syrians die in other heinous ways. But there is something especially cruel about these weapons: they are silent killers.
Victims can't smell or see the enemy coming, and then they are hyperventilating while their corneas burn and their lips turn blue.
Chemical weapons have been outlawed for good reason for almost a century. Their use is a serious violation of international law. An artillery shell the size of a suitcase, full of sarin gas, is lethal enough to wipe out an entire football stadium of civilians. It is the poor man's weapon of mass destruction.
Had the US and its allies failed to act, it would have set a dangerous precedent. A message would have been sent not only to Assad but to other rogue regimes that use of chemical weapons has no serious consequences. That the UN's responsibility to protect - the principle that if a state is no longer willing or able to protect its own population, it becomes the international community's responsibility to do so - is nothing but a hollow promise.
The use of chemical weapons is not the UK's red line. It is not a Western construct. It is the red line of the free world, and action was needed to protect against the proliferation of these monstrous killers. The Unites States, in partnership with Britain and France, deserves credit for taking on this daunting challenge. (© Daily Telegraph, London)
Julie Lenarz is an expert on Islamic terrorism and extremism at the Human Security Centre, a London-based thinktank.