Responding Monday to new U.N. sanctions, North Korea threatened a nuclear attack on the United States.

Speaking at the ASEAN summit in Manila, North Korea's foreign minister spoke of "intercontinental attack capabilities" that meant his nation could teach the U.S. a "severe lesson with its nuclear strategic force." Doubling down, North Korea's state news agency suggested that "There is no bigger mistake than the United States believing that its land is safe across the ocean."

In the context of North Korea's rapidly advancing intercontinental ballistic missile program, these threats cannot be ignored.

Still, North Korean officials would do well to remind themselves of the nuclear threat they currently face.

Because at this very moment, there are probably at least two Ohio-class US nuclear ballistic missile submarines on patrol in the Western Pacific. Their mission? To provide surety for the nation's strategic nuclear deterrence posture. Supporting U.S. land based and air launched nuclear missile forces, the SSBNs move slowly in a variety of pre-defined patrol sectors far out at sea.

Under the military's nuclear attack base plan, OPLAN 8010, the SSBNs stand ready to launch their Trident D-5 ballistic missiles at either preselected or actively chosen targets.

Regardless, the SSBNs represent the pinnacle of warfighting lethality. With each SSBN armed with 24 missiles and at least 8 independent nuclear warheads per missile, one US Ohio-class submarine carries at least 192 nuclear warheads varying between yields of 100 and 475 kilotons. Moreover, as the Bulletin of the Atomic Scientists blog noted in March, these missiles possess exceptionally accurate targeting systems.

This reality is one North Korean leaders must constantly bear in mind. After all, were North Korea preparing a nuclear strike on the U.S. homeland or a territory such as Guam, the response would be swift and overwhelming. In that scenario, the US would likely launch a pre-emptive decapitation strike on Kim Jong Un's regime.

What would that mean?

Well, consider the NukeMap below. It shows the projected destructive impact of a 475 kiloton warhead on the North Korean capital, Pyongyang.

But that's just the start. Were a North Korean nuclear attack looming, the U.S. military would almost certainly recommend Trump to authorize 3+ warhead strikes on each major command and control target. Depending on U.S. concerns about civilian casualties and the imminence of the threat, that might include multiple strikes on Pyongyang itself. Missile launch sites, carriers, and warhead silos would also definitely be targeted in such an event.

This is what Sen. Lindsey Graham, R-S.C., was talking about when he recently described "destroying North Korea itself."

Although diplomacy should be the absolute priority in addressing Kim Jong Un's ballistic missile program, Kim should have no illusions. The nuclear threat game that he's engaged in is not one that would end well for him if the threats were ever carried out.