Critics of President Barack Obama, including President Trump, say

Critics of President Barack Obama, including President Trump, say
that his decision not to enforce his “red line” on chemical attacks in 2013 convinced the Assad government it could get away with anything, and that it has been escalating its harsh tactics against civilians ever since.
After Mr. Trump came into office, proclaiming a wish to work with Russia and maybe even Mr. Assad against the Islamic State, expectations grew
that the international community would accept relegitimizing Mr. Assad.
Since that “green light,” wrote Jihad Yazigi, an opposition-leaning Syrian economist, “Assad knows
that a large-scale attack against its civilians is a short-term public relations liability but a long-term political asset.”
That was only reinforced, critics say, by recent statements by American officials
that it was time to accept the “political reality” of Mr. Assad’s grip on power.