The U.S. has more than 28,000 troops stationed in South Korea and around 50,000 American personnel in Japan. There also are more than 6,000 troops in Guam.
As things stand now, Wit isn't so sure the U.S. has the capability to destroy all the missiles in North Korea or to defend against "large salvos" of rockets.
"It would be very difficult if the North Koreans for some reason started launching large numbers of missiles to deal with it," said Wit. "A lot of them would get through."
Then again, the Joint Chiefs chairman also said at the Aspen event that there's concern about the ability of North Korea to ramp up its missile capacity and development. He also pointed out that the regime of Kim Jong Un also has stepped up its missile testing and conducted several nuclear tests last year.
"Our concern is the growth in capacity that has increased numbers of missiles over time and the combination of an intercontinental ballistic missile and nuclear weapons obviously concern us," said Dunford.
The general added, "Do the American people need to be concerned long term? Yes. This is probably at the top of everybody's inbox in national security today ... dealing with the North Korea crisis. But we can protect the American people today and that I am sure."
NBC News' chief foreign affairs correspondent, Andrea Mitchell, moderated the discussion with the general and asked how the U.S. does a pre-emptive strike on North Korea when it probably doesn't know where all the weapons are located due to tunnels, underground nuclear facilities and other measures it is believed to take.
She asked about military options planned but Dunford said the U.S. was now focused on a so-called pressurization campaign using primarily economic and diplomatic pressure to denuclearize the Korean Peninsula.
Secretary of State Rex Tillerson is working to get the international community to back more of these measures, Dunford said. He added that the U.S. military supports that effort because military options could lead to something perhaps "horrific. It would be a loss of life unlike any we have experienced in our lifetime."
Also, the general said he is assuming North Korea already has the ICBM capability. Earlier this month, North Korea test-fired a missile it claimed was a long-range missile capable of reaching the U.S.
"In the business I'm in, I get paid to assume that they have that capability now," Dunford said. "So I have a sense of urgency to assume they're going to have it. In my judgment it's academic whether it's six months, 12 months, 18 months or 24 months from now. They're on a path — and it seems a irreversible path — to develop that capability. And so we need to have a sense of urgency to denuclearize the Korean Peninsula, which is our U.S. policy right now."