Most of the world woke up Wednesday to reports of a possible chemical weapons attack by Syrian forces in the eastern suburbs of Damascus. Graphic video and firsthand accounts soon emerged that appear to support these claims with numerous victims, including several children, dead from apparent asphyxiation and showing no other injuries. While the total death toll remains unclear, if these allegations are true it will be the worst chemical weapons attack since the notorious Halabja massacre committed by the Iraqi government in 1988. The attack also comes just days after a U.N. inspector team arrived to investigate three other allegations of chemical weapons use and a year, almost to the day, after Obama surprised the White House press corps with an impromptu briefing where he proposed his now infamous "red line" on Syria.

At this point it is clear that the red line was crossed long ago. Between February 2012 and June 2013, there were at least 18 incidents where chemical weapons were said to be used. Most of these allegations are against the Syrian regime, but there are also accusations against the rebels and the various Islamist militant groups that have joined the fray. These allegations give new dimension to a conflict that is already the world's worst humanitarian disaster in 20 years.

Use of chemical weapons is strictly prohibited in conflict under the Chemical Weapons Convention and customary international law. Although several governments have experimented with developing chemical weapons, their use has been limited since World War II. Very few acts in wartime garner the same condemnation as chemical and biological weapons, and making accusations of their use is highly controversial. When the Syrian conflict started in 2011, world leaders noted their concern over the possible use of chemical weapons and repeatedly stated that such use would be unacceptable. But the allegations have come and gone with very little change to show for it.

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