Preparing for such an attack would entail amassing naval carrier groups in the area — which would take a minimum of 30 days — and transferring land-based aircraft to bases in South Korea and Japan, according to Scott.
Campbell cautioned that even after a large-scale attack, "the North Koreans will still possess tremendous capabilities to respond and destroy Seoul." Scott said the best thing would be if the North Koreans moved first, "because then they move out of their positions and we have configured our military for years to fight a defensive battle for South Korea."
North Korea Response: Diplomacy or Provocation
Next, Nightline asked Taylor and Cha how North Korea might respond to a massive buildup of U.S. ships and war planes in the region, and the threat of attack in the event of any suspicious plutonium movements.
Taylor said the North Korean regime's first reaction would be diplomatic: to ask its historical allies China and Russia to put pressure on the United States to back off from unilateral military action. He suggested China could heighten its military readiness across the sea from Taiwan.
Cha said the North Koreans would likely match the U.S. mobilization, saying they were doing so in response to the Americans. Then, he said, judging from "North Korean negotiating behavior" in the past, the North would call the Americans' bluff and move some plutonium to escalate tension and "put the ball back in the United States' court."
Attack Across the DMZ
Assuming that the United States responded to the plutonium movement with pinpoint attacks on one or more of its nuclear facilities, Taylor said North Korea would respond with "overwhelming strikes," using long-range artillery and multiple-rocket launchers armed with chemical and biological weapons to turn Seoul into what the official North Korean media have been calling "a sea of fire."
Taylor said the North Koreans, believing the Americans would not tolerate high losses, would aim to immediately "give them large numbers of casualties like they've never seen before."
Cha agreed that North Korea, if attacked by U.S. strikes, would respond with a massive artillery attack on Seoul. "The way the balance of forces are on the Korean peninsula, the North Koreans are in a 'use or lose' situation. In other words, they have to use them first or they're going to lose them in battle," he said. He also said the North Koreans might try to stop the flow of U.S. reinforcements by using long-range missiles to knock out U.S. facilities in Japan.
Possibility of U.S. Nuclear Attack Seen
If North Korea waged an all-out attack on the South, Scott said it would be "a war the likes of which we haven't seen since World War II, if then." North Korea has a substantial air force and an army of more than one million men, with reserves of about four and a half million.
If the North Koreans used biological and chemical weapons against U.S. troops or South Korean targets, Scott said he would advise the U.S. president to respond with tactical nuclear weapons, provided there were suitable targets. Campbell said he would recommend a last-minute diplomatic appeal to China and Russia before using nuclear weapons.
Would the North Back Down?