"We train harder here than in any other unit we have been in and we do that because we know we have to be ready, we're the only ones that can do it so we're prepared and it is very real," says Lt. Col. Adam W. Hilburgh, commanding officer of the battalion the largest of its kind in the U.S. military.
Allowing CNN exclusive access to a training drill underground, four members of the battalion enter a facility staged to look like it's for nuclear weapon storage.
Suited in "Level B" protective suits, chemical resistant boots and gas masks attached to oxygen tanks on their backs, they take no chances. They send a remote-controlled robot ahead to monitor radiation levels and chemical agents. The team then moves in and discover yellowcake -- a form of uranium -- a substance North Korea is believed to possess.
It is a scenario that is staged, but based on reality. "We take into account the newest intelligence to tailor our training to ensure we're ready for anything that they could possibly have or use on the battlefield," says Lt. Col. Hilburgh.
Staging drills deep underground also makes the training more realistic. Many of North Korea's nuclear and chemical facilities are believed to be below ground, out of sight of satellites.
Sgt. Cameron Armstrong is one of the team being put through his paces in this drill. "Going into North Korea, it's pretty likely that the mountainous terrain will provide caves and underground facilities for them to be utilizing as weapons facilities," he says.
Being here, so close to the potential threat, is a compelling reason for this battalion to be based here on the Korean peninsula. Returning to South Korea in 2013 after an eight year absence, members of the battalion say the proximity to potential nuclear material makes their training far more real.
Sgt. Michael Thron is part of a four-man crew manning a specially-modified Stryker armored vehicle, which can detect chemical elements up to two miles or three kilometers away.
Speaking about the importance of being based in South Korea, he says, "Not only does it make it more crucial but it makes it more realistic and it helps us keep our focus."
A focus that is currently on North Korea's nuclear ambitions, but 1st Lt. Greg Moxcey, a chemical response team leader, cautions against dismissing Pyongyang's chemical capabilities.
"Chemical weapons are probably the greater concern," he says.
"Because you have no idea where they can be used and how many there possibly are."