A war with North Korea would involve the mobilization of that country’s entire population and the activation of at least 1.2 million active-duty soldiers and 7.7 million reservists. North Korea would then implement plans which the regime designed to fight — and defeat — U.S. forces on the battlefield. This does not mean North Korea would succeed. One of the biggest problems the North Korean army faces is lack of ability to sustain itself — particularly in terms of fuel, which would limit the ability of its tanks and other armored vehicles to advance south of Seoul, the South Korean...