While Americans were busy enjoying the July Fourth holiday, news broke that North Korea had crossed another military milestone: its first successful test of an intercontinental ballistic missile. This missile, the kind that could theoretically be tipped with a nuclear warhead, could travel far enough to hit Alaska.

That’s pretty worrying in and of itself. But the North Korean crisis is even scarier than you think.

That isn’t because the country’s supreme leader, 33-year-old Kim Jong Un, is totally irrational — a “crazy fat kid,” as Sen. John McCain once termed him. Instead, it’s that the impoverished North Korean regime is deeply insecure, so worried about its own survival that it is willing to go to dangerously provocative lengths to scare the United States and South Korea out of any potential attack.

When you combine this insecurity with the opaque nature of the North Korean regime, you have a situation that could easily spiral into outright conflict in the event that one of North Korea’s frequent military provocations (like the missile test) goes awry. Given North Korea’s massive conventional military and unknown number of nuclear weapons, conflict on the Korean Peninsula would cost hundreds of thousands, if not millions, of lives.

That’s not to say that war between the US and North Korea is likely, even after the new missile test. It isn’t. Rather, it’s that the risk of a catastrophic conflict is much higher than anyone should feel comfortable with, arguably more likely than anywhere else in the world.

Here at home, many are preoccupied with the fight against ISIS and, before that, the Iranian nuclear program. North Korea gets far less public attention, but it is a literally existential threat to two of America’s closest allies, Japan and South Korea. And it doesn’t seem like there’s any solution in sight.

North Korea’s government is weak and unpredictable

To understand why North Korea is so unstable, we need to start with something counterintuitive: North Korea is really weak.

Pyongyang is one of the world’s poorest countries. Its GDP per capita is estimated at about $1,000, about 1/28th of South Korea’s. It faces chronic shortages of food and medical supplies, depending on Chinese aid to meet its citizens’ basic needs. There’s a real risk that the Kim regime collapses under the weight of its own mismanagement.

Nor is the North secure from military attack. While its army is extremely large personnel-wise, with about 1.2 million soldiers, it uses antiquated Cold War technology while its neighbors to the South are equipped with top-of-line modern gear. Moreover, the presence of 23,500 US troops in South Korea means any war between North and South Korea would draw in the world’s only superpower, though with potentially enormous American casualties.

Facing the twin dangers of domestic instability and foreign attack, the North has devised a strategy for survival that depends (somewhat counterintuitively) on provoking the South and the United States.

The North will do something that it knows will infuriate its enemies, like testing an intercontinental ballistic missile or shelling a South Korean military base. This limit-pushing behavior is designed to show that the North is willing to escalate aggressively in the event of any kind of action from Washington or Seoul that threatens the regime, thus deterring them from making even the slightest move to undermine the Kim regime. It also sends a signal to the North Korean people that they’re constantly under threat from foreign invasions, and that they need to support their government unconditionally to survive as a nation.

The problem is that this strategy is inherently unstable. There’s always a risk that one of these manufactured crises spirals out of control, leading to a conflict that no one really wants. This is especially risky because the North Korean government is deeply insular: Washington doesn’t have the kind of direct line of communication with the North that it had with the Soviet Union during the height of the Cold War, which was vital in preventing standoffs like the Cuban Missile Crisis from escalating.

Maybe the Trump administration responds too aggressively to a provocation, prompting North Korean retaliation. Maybe North Korea thinks it’s about to be invaded by the South, leading it to mount a preemptive strike. Maybe South Korea misreads the North’s signals and thinks it is about to launch a war, causing the South to do something wild like try to assassinate Kim Jong Un. That isn’t totally hypothetical: Jeffrey Lewis, director of the East Asia Nonproliferation Program at the Middlebury Institute of International Studies and a noted North Korean expert, thinks killing Kim is a real option that the South is considering if it thinks war is likely (mainly to head off a nuclear strike before it starts).

These scenarios illustrate that a basic truth: A situation where one side is constantly provoking the other is extremely volatile. There are lots of ways for things to go wrong, all of which stem from the fundamental insecurity of the North Korean regime.

“In North Korea at least, everything is organized around the fear that they will be invaded, and that Kim Jong Un will end up like Muammar Qaddafi in Libya or Saddam Hussein in Iraq,” Lewis told Vox in an April interview. “It’s easy to see how things could get out of hand in a hurry.”

War could cause millions of casualties — even before nukes

Here’s what makes this all really worrying: While North Korea is in a weak position relative to its enemies, it is still objectively a relatively strong military. While South Korea and the United States would almost certainly defeat the North in the event of a conflict, the cost of such a war would be incredibly high.

The North Koreans are not stupid: They know they’re militarily outclassed by their enemies. So their strategy in the event of an out-and-out war, as far as outside analysts can tell, is to inflict overwhelming pain as quickly as possible: to bombard South Korea, Japan, and any American forces they can find with missiles and artillery to the point where their stronger enemies lose their appetite for a protracted conflict.

The estimates of a conflict involving the North’s non-nuclear arsenal alone are hard to fathom. My colleague Alex Ward spells some out:

South Korea’s capital city, Seoul, is a so-called “megacity” with a whopping 25.6 million residents living in the greater metropolitan area. It also happens to be within direct firing range of thousands of pieces of North Korean artillery already lined up along the border, also known as the demilitarized zone. Around 70 percent of North Korea’s ground forces are within 90 miles of the DMZ, presumably ready to move south at a moment’s notice. Simulations of a large-scale artillery fight between the North and South produce pretty bleak results. One war game convened by the Atlantic back in 2005 predicted that a North Korean attack would kill 100,000 people in Seoul in the first few days alone. Others put the estimate even higher. A war game mentioned by the National Interest predicted Seoul could “be hit by over half-a-million shells in under an hour.”

Here’s an even grimmer statistic: A South Korean simulation conducted in 2004, before the North had developed nuclear weapons, estimated that there could be up to 2 million casualties in the first 24 hours of a conflict.

Obviously, the death toll would be exponentially higher if North Korea used any of its nuclear weapons. Those could potentially destroy Tokyo, Seoul, or other cities in the two countries.

It’s not clear how many working nuclear weapons the North has, though estimates suggest around 10 to 16. We do know that the North’s missiles have enough range to reach Tokyo, and that the North has tested a nuclear weapon designed to fit on precisely such a missile.

Best guesses suggest the North would try to nuke US forces in the region, to attempt to limit America’s ability to help South Korea in ground combat on the Korean Peninsula. But Pyongyang could also target population centers as well — despite the likelihood that any such attack would invite nuclear retaliation from the United States, which has mutual defense agreements with both Japan and South Korea.

“Its rhetoric and accelerated pace of missile testing suggests that North Korea would be the first to use nuclear weapons if it believed itself to be under attack,” Mark Fitzpatrick, the executive director of the International Institute for Strategic Studies America think tank, writes. “Its nuclear posture incorporates the ‘use them or lose them’ principle.”

The situation is getting more dangerous and shows no signs of improving

As bad as things are with North Korea right now, the situation will only get worse over time. North Korea’s mastery of nuclear technology — meaning both missiles and nuclear devices themselves — is steadily improving.

The country’s fifth nuclear test, in 2016, is estimated to be about 33 percent more powerful than the bomb that leveled Hiroshima. If its missile program continues unabated, North Korea will eventually be able to hit the whole of the United States.

Previously, the North has threatened to “wipe out Manhattan” in the event of conflict with the United States. This threat is empty now — but absent some kind of brake on North Korea’s nuclear program, it may well become quite serious.

Hence why discussions about North Korea in Washington have taken on such an urgent tone. The United States wants to head off the growth of North Korea’s nuclear program before it becomes a threat to the American homeland, but right now it has no clear strategy for doing that.

The best bet so far has been to get China to pressure North Korea economically. While North Korea is exceptionally isolated economically — the US has basically sanctioned the North as much as it can — China remains the North’s economic lifeline.

But so far, the Chinese haven’t played ball: Trade between China and North Korea actually increased in the first quarter of 2017, allowing the Kim regime to continue puttering along. The US government can try to punish China, through things like sanctions on Chinese banks that do business with Pyongyang, but there’s no guarantee that this will be enough to cause China to reverse its stance.

What’s more, any agreement would only head off a threat to the US homeland from North Korean missiles. There’s no chance, according to Lewis, that the US could convince the North to give up its nuclear weapons altogether — or end the provocations that create the risk of conflict in the first place.

Absent some kind of agreement with the North, which seems far off, the only way to lessen the threat would be for the regime to collapse. While this is a possibility, it seems pretty remote at the moment. North Korea’s economy is growing fast by its standards, which would make a popular rebellion less likely. And there aren’t obvious signs of a brewing rebellion from the North Korean elite.

Plus, a regime collapse would create its own challenges: a governance vacuum in an impoverished country of tens of millions. This is a problem in both humanitarian terms — many of these people are already effectively starving — and security ones. How do you prevent the weapons that made up the North Korean government’s arsenal, both nuclear and conventional, from falling into the wrong hands?

The bottom line is that the North Korean situation holds perhaps the greatest risk of a nuclear war of any conflict on earth. The American public is preoccupied with the fight against ISIS and the unending stream of Trump scandals, but we ignore North Korea at our own peril.