Jet-lagged from a long overseas trip, Defense Secretary Chuck Hagel had just sat down with his wife for a quiet dinner at an upscale Italian restaurant in northern Virginia when his phone rang. It was the White House on the line. President Barack Obama wanted to speak with him. It was Aug. 30, 2013, and the U.S. military was poised for war. Obama had publicly warned Syrian strongman Bashar al-Assad that his regime would face consequences if it crossed a “red line†by employing chemical weapons against its own people. Assad did it anyway, and Hagel had spent the day...