The U.S. tends to avoid talk of a first strike against North Korea but pre-emptive action called the "Kill Chain" is part of the official and public national defense strategy of South Korea.
The stark difference between Seoul and Washington on the ultimate form of deterrence against North Korean dictator Kim Jong-un is an example of the many issues in dispute in the once-solid U.S.-South Korea alliance.
Those differences will the subject of "frank and serious" discussions in White House talks between President Donald Trump and new South Korean President Moon Jae-in, a senior White House official said on background Wednesday.
Moon, a 64-year-old human rights lawyer elected in early May, arrived in Washington Wednesday. His first stop was at the National Museum of the Marine Corps in Quantico, Va., where he will join with Gen. Robert Neller, the Marine Commandant, to honor those who fought in the Korean War battle at the Chosin Reservoir in 1950.
Moon's parents were among the refugees who were evacuated from Hongnam in North Korea to South Korea after the battle.
Trump and Moon are to hold their first face-to-face meeting at the White House Thursday followed by dinner. At the top of the agenda is "the very urgent threat" posed by North Korea's missile tests aimed at developing a nuclear Intercontinental Ballistic Missile capable of hitting the U.S. mainland and its buildup of conventional forces, the senior White House official said.
"There will be some differences in the way they want to approach that. That's fine," the official said of Trump and Moon, but the two were on the same wavelength as to "overarching goals," meaning the dismantlement of the North's nuclear and missile programs.
Moon has expressed an openness to dialogue with the North under the "right conditions." During the campaign, Trump called Kim Jong-un a "bad dude" and a "maniac," but also said he might be willing to meet with Kim over a hamburger to defuse tensions on the peninsula.
"I don't think that is necessarily a major point" of contention, the official said of the THAAD deployment. Two of the six launchers in a full THAAD battery are now in place on a former golf course south of Seoul. The official said Moon had already said deploying the full battery was not a "reversal" on THAAD but rather a pause to allay environmental concerns.
The official did not discuss potential military options against North Korea, saying that Trump for now was focused on ratcheting up diplomatic and economic pressure on the North "to change their calculus. Right now we see no evidence" that Kim Jong-un was backing away from developing a nuclear ICBM "explicitly designed to threaten America," the official said.
The question then is what the U.S. and South Korea would do once the North developed the capability and a suspected ICBM was sitting on the launch pad.
Retired Army Gen. Walter Sharp, the former commander of U.S.-Forces Korea and the United Nations command, ventured an answer last December -- attack the missile site.
The missile should be destroyed, Sharp said, and the U.S. must also be ready to respond with overwhelming force if North Korea retaliated. "If he (Kim) responds back after we take one of these missiles out," Kim should know "that there is a lot more coming his way, something he will fear," Sharp said.
"I think we're to that point that we need to have that capability. I am to that point," Sharp said. He said the U.S. could not risk relying solely on anti-missile defenses to counter North Korean long-range missiles
Sharp spoke at a panel discussion on challenges from North Korea at an all-day forum sponsored by the Center for Strategic and International Studies on the national security issues would confront Trump.
Others on the panel, while sharing Sharp's concerns about the North Korean nuclear threat, worried about the aftermath of a pre-emptive strike. Despite North Korea's nuclear tests, "there is potential in diplomacy," said Christine Wormuth, the former undersecretary of Defense for policy in the Obama administration.
"I'm concerned about pre-emptive action on the launch pad," Wormuth said. "What does Kim Jong-un do in response? I worry quite a bit about our ability to sort of manage a potential retaliation."
Defense Secretary Jim Mattis and Joint Chiefs Chairman Gen. Joseph Dunford were also worried. "It would be a war like nothing we have seen since 1953, and we would have to deal with it with whatever level of force was necessary," Mattis told the House Armed Services Committee in June 12 testimony.
"There's 25 million people in Seoul, and 300,000 of those are Americans who are within range of thousands of rockets, missiles and artillery pieces along the border," Dunford said.
"I don't have any doubt in my mind, if we go to war with North Korea, that we will win the war," he said, but he warned that "we will see casualties unlike anything we've seen in 60 or 70 years."
Dunford said that the bulk of the casualties would come "in the first three, five, seven days of the war, where all those people in the greater Seoul area are exposed to the North Korean threat that we will not be able to mitigate initially."
Since the 1953 armistice on the peninsula, the Pentagon, the service branches, the Army's Training and Doctrine Command (TRADOC), South Korea's Ministry of Defense and the think tanks have gamed out how a war with North Korea would progress. Their analyses vary little from Dunford's blunt assessment on the opening stage of a conflict
A 324-page white paper issued by South Korea's Ministry Defense on Dec. 31, 2016, outlined a three-pronged strategy against the North to begin with a pre-emptive strike to stop what was perceived as an imminent attack.
"In the face of gradually increasing nuclear and missile threats from North Korea, the ROK (Republic of Korea) military is strengthening its deterrence and response capabilities. A three-axis system composed of the Kill Chain, Korea Air and Missile Defense (KAMD) and the Korea Massive Punishment and Retaliation (KMPR) strategy is being put in place," the paper said.
The Kill Chain would launch a series of air, naval and missile strikes to prevent an imminent attack on Seoul. To back up the Kill Chain, South Korea was also considering the lease of a reconnaissance satellite, possibly from Israel or other countries, to obtain information independently from the U.S. on a possible imminent attack from the North, a Defense Ministry official told the Korea Times.