The demand for regime change by the US, the EU, and NATO torpedoed the United Nations effort for a diplomatic solution. The Assad regime had no stake in a peaceful resolution, since it would mean its ouster in any case. And the opposition knew it need not respect a ceasefire, since everyone who supports them supports regime change.
It was into this situation that Turkey flew an F-4 Phantom through Syrian airspace. Exactly what did Ankara think Syria would do? On the other hand, maybe it knew exactly what Syria would do.
Conn Hallinan can be read at dispatchesfromtheedgeblog.wordpress.com and middleempierseries.wordpress.com