Pentagon Responds to Query From Congressmen on a Korean War II - airstrikes not enough

On 27 October 2017,Rear Admiral Michael J. Dumont,US Navy,responded to a letter from Representatives Ted Lieu (D-California) and Ruben Gallego (D-Arizona),who asked the Department of Defense to scope out a possible armed conflict with North Korea for them.They were particularly interested in the expected casualty assessment and the prevention of North Korean retaliation.
RADM Dumont replied that:
We have not seen any change in the offensive posture of North Korea's forces,something we watch very carefully.We remain postured to respond in the event of a provocation or conflict,and we have taken all appropriate measures to protect our Allies,the ROK and Japan,and US Forces in those countries.As military professionals,we prepare for all contingencies and continually review our posture and coalition efforts to deter and respond,if necessary,using the full range of military capabilities.*
Calculating even the roughest "best-or worst-case casualty estimates " for any conventional or nuclear attack is challenging.We continually evaluate what actions North Korea might take,and its capability to attack the ROK,Japan or Guam,and in particular Seoul,with long-range artillery,rockets,and ballistic missiles.In addition to being the capital and the ROK's most densely populated city,Seoul is also just 35 miles from the demilitarized zone.Given Seoul's vulnerability,casualty estimates will vary significantly depending upon the nature,intensity,and duration of a North Korean attack.
Further complicating casualty estimates,is the ability of our ROK-US Alliance Forces to respond to a North Korean attack with counter-battery fire and coalition airstrikes,missions for which we train constantly.We can help mitigate the number of casualties and reduce the duration of  a North Korean attack by maintaining the readiness of our forces and our ability to respond rapidly and decisively.*
The only way to "locate and destroy-with complete certainty-all components of North Korea's nuclear weapons programs" is through a ground invasion.A classified briefing is the best venue for a detailed discussion of our capabilities to counter North Korea's ability to respond and to eliminate North Korea's nuclear weapons located in deeply buried,underground facilities.We would be happy to join the Intelligence Community to address these issues in a classified briefing,RADM Dumont offered.*
President Donald Trump is currently traveling through East Asia to meet with South Korean and Japanese leaders,as well as President Xi Jinping of China,on the North Korea crisis.