Defense Secretary Jim Mattis hinted that the United States still had military options left for dealing with North Korea, but did not elaborate when asked for details Monday. Most experts think a military strike on North Korea would invite a devastating response from Pyongyang. The city of Seoul, South Korea, home to 25 million, is well within artillery range of the North, which would most likely use conventional artillery munitions and chemical weapons. But according to Mattis, the Pentagon has a few tricks up its sleeve that wouldn't involve the decimation of Seoul.