Tillerson's comments were unusual, however, as he appeared to be implying, in public, that the U.S. would consider military force as a way of preventing an attack by Pyongyang, and not just as a means of retaliation. It also comes amid a greater sense of urgency about the threat because of North Korea's rapid progress toward developing the means to strike the U.S. with a nuclear-tipped missile. Risks of military action are high as North Korea could unleash a massive artillery barrage on Seoul in retaliation.