Leon tells only half the story and implies/judges Obama in a simplistic analysis that leaves out facts, balance, and reality.
Fact - partnering with Russia to remove chemical weapons decreased a significant holocaust - as bad as Aleppo is, think if Assad had the use of chemical weapons
Fact - it is always easy to argue black and white - sorry, not the situation in Aleppo or Syria
Fact - what failed was partnering with Russia to prevent Aleppo - Russia reneged on successive offers.  What does Leon suggest as an alternative?
What he argues for was tried over and over again - what did we learn?  Made the situation worse and led to increased violence and deaths.
Fact - focusing on ISIL has saved lives - just not in Aleppo.....so, is an Aleppo live worth more than a Yadzi life?