On Thursday, President Donald Trump told Reuters, “There is a chance that we could end up having a major, major conflict with North Korea. Absolutely.” He essentially threatened to launch a pre-emptive attack on North Korea if intelligence shows they develop the capability to launch a nuclear inter-continental ballistic missile (ICBM) that could hit the United States.

The day before Trump made his open threat, all 100 senators went to the White House to receive a classified briefing on North Korea presented by the secretary of state, secretary of defense, chairman of the joint chiefs of staff, and director of national intelligence. Members of the House were briefed later.

Unlike his strikes in Syria, Trump can legally attack North Korea at-will because the United States is still technically at war with North Korea. The cease-fire that began in 1953 can be broken at anytime.

The current showdown comes after years of increasing tensions. Peace and reunification talks have been deteriorating since 1953, but when North Korea was famously publicly condemned by President George W. Bush as being part of an “Axis of Evil,” the regime began a crash nuclear weapons program that culminated in a successful nuclear weapons test in 2006.

In 2009, North Korea conducted a second successful nuclear weapons test, which was followed by other tests in 2013, 2016, and 2017. There is no doubt the North Korean government has the capacity to detonate a nuclear weapon.

It appeared that, while unhappy, the U.S. and North Korea’s neighboring countries could live with a nuclear North Korea. But corresponding to its nuclear weapons’ capacity, North Korea has also been developing and launching ballistic missiles that could carry a nuclear payload to distant shores. Even, in theory, Hawaii and the continental United States.

That threat, not surprisingly, is not tolerable to the United States. A president more seasoned and restrained than Trump would almost certainly take the identical position. If North Korea develops an ICBM capable of carrying nuclear weapons that can his the west coast of the United States, there will almost certainly be a U.S. attack on North Korea.

Given the trajectories of the North Korean government’s ambition and the United States’ commitments, war seems increasingly likely, and soon. The consequences of that war will be catastrophic for South Korea. Its largest city, Seoul, is within range of North Korea’s massive number of artillery weapons already targeting the city. Those conventional weapons would be enough to level that city, where over 10 million people reside.

If North Korea is able to deploy its nuclear as well as its conventional capabilities, other parts of South Korea and possibly Japan could also face immense if not complete destruction.

But before it all goes to black, it is worth considering the dynamics that got us to this point. In a recent interview with Shadowproof, China expert Peter Lee explained U.S. involvement in the Korean Peninsula has been far from benign or conducive to peace and unity.

“Once the North Korean threat is diminished by a peace treaty, South Korea has a lot less reason to be an enthusiastic member of the U.S. alliance,” Lee said.

“Basically, South Korean economics and diplomacy is now dominated by China. And what keeps the United States hanging on there, and keeping South Korea from switching to a pretty much Chinese alignment, is the fact that the United States is the security provider for South Korea and South Koreans are pretty worried about the North Koreans doing something goofy to them.”

Lee said there are two reasons why the U.S. has “really slow-walked peace negotiations” with North Korea. “One reason is once you got the North Korea threat—you can keep a lot of allies and military gear in North Asia to contain China, while pretending it’s about North Korea. But the other reason is that when there is peace with North Korea, the U.S. loses its mission in South Korea.”

For the U.S., North Korea has been a convenient foil to justify the American military presence in the region, which ensures U.S. businesses have access to Asian markets. It is a good game as long as it lasts—neither peace nor outright war, but a status quo that ensures U.S. power and influence despite a rising China.

But now, it looks as though that game may be ending. The failure—or, as the case may be, disinterest—to find a peaceful resolution to the Korean War in past decades, combined with belligerent rhetoric, produced present conditions for an outright military confrontation.