How did Bashar al-Assad, a mild-mannered ophthalmologist, become a ruler who uses chemical weapons against his own people? And why is President Trump rejecting Mr. Assad, even as he is embracing another Middle Eastern leader with a reputation for brutality. Guests: Ben Hubbard, who covers the Middle East for The Times; Rukmini Callimachi, who writes about the Islamic State. For more information on today’s episode, visit http://nyti.ms/2p79Cur.

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