In the past few days, North Korea has challenged its many adversaries with a series of provocative actions. It has launched a rocket, restarted a reactor that could fuel nuclear weapons and it claims to have tested a hydrogen bomb. That's created anxiety from Asia to Capitol Hill. How are its many adversaries responding to these "destabilizing and provocative actions?" We ask Jonathan Pollack, a senior fellow in the John L. Thornton China Center and the Center for East Asia Policy Studies at the Brookings Institution. He's also the author of No Exit: North Korea, Nuclear Weapons and International Security.