This cartoon by Chappatte from "Le Temps" relates to reports that the Syrian government has used chemical weapons against rebel forces.
BACKGROUND
President Barack Obama warned the Syrian regime on Friday that proof it had used chemical weapons on its civilian population would be a "game-changer", but cautioned that more evidence was required.
Speaking at the White House, Obama said that confirmation Bashar al-Assad had deployed chemical agents in the protracted Syrian civil war would alter his administration's "calculus", but stopped short of declaring that a "red line" had been crossed.
Obama's cautious comments reflected the lack of a consensus in Washington over how to respond to claims that Syria has used sarin gas in recent incidents. [Source: The Guardian]
THE CARTOON
Syrian president Bashar al-Assad, armed with chemical weapons and wearing a gas mask, is shown crossing a series of red lines which carry increasingly stern warnings. Meanwhile Obama and an American general look on without intervening.
COMMENTARY
The cartoonist uses a graphic representation of the idiom 'cross a red line' (see definition below) to highlight Obama's reluctance to take action over Syria. Apparently, Obama has threatened Syria a total of seven times now using the "red line" metaphor, a fact pointed out by Bob Englehart in the commentary on his cartoon, which also uses the red line idea. As does this cartoon by Marian Kamensky. And this one by Schrank from The Independent.
IDIOM
A red line is an issue or a demand that one person or group refuses to change their opinion about during a disagreement or negotiations. • The issue of sovereignty is a red line that cannot be crossed.