Since 2006, every three years or so, North Korea blows up a nuclear bomb. But on Sept. 9, it tested a nuclear bomb in fewer than nine months since its last such test.

One would expect this nuclear bomb to be a bigger one. But, to confuse matters further, it wasn’t. Based on the magnitude of the earthquake the nuclear test caused experts believe the bomb’s yield was a little more than 10 kT—about the size of the bomb the US dropped on Hiroshima in 1945.

What was North Korea trying to do? One possible answer is that the nuclear bomb was detonated as part of the 68th-anniversary celebrations of North Korea’s founding day. Or that, on an opportune day, it was an attempt to get the attention of world leaders who had attended the recent G20 and ASEAN meetings in the nearby countries of China and Laos.

The test did get attention, but it was not much different from that given to the previous nuclear tests. The US warned of “serious consequences.” South Korea called it “fanatic recklessness.” China urged North Korea to not ”worsen the situation.”

But experts warn that it’s time we stop taking North Korea lightly and that we act before it’s too late. The latest test, they say, is part of a much bigger plan. The rogue state is creating a nuclear program that could make it impossible for the US and allies to defend against. Worse still, North Korea is advancing its technology in such a way that could soon produce nuclear bombs and sell them to other rogue states, such as Syria, Iran, and Pakistan.

Surviving as a nuclear state

The US and its allies have tried for many decades to bring North Korea to the negotiating table. Out of fear that the rogue regime would develop nuclear weapons, the US even got the country to the sign the Non-Proliferation Treaty (NPT) in 1985. When the terms of the NPT were no longer acceptable to North Korea, in 1994, the US gave it aid in return for agreeing to freeze its plutonium program.

None of those sanctions has really worked.

Finally, when the aid stopped coming in and no more was coming, North Korea broke all NPT rules and began its nuclear program in earnest in 2003. In less than three years, North Korea had developed and tested its first nuclear bomb. In response, the United Nations levied sanctions on North Korea to try to stop the country from developing its arsenal even further.

None of those sanctions has really worked. If anything, there has been a step change in North Korea’s plan to become a nuclear-weapons state. Between 1994 and 2008, the country conducted 16 missile tests and one nuclear test, according to the data collated by the Centre for Strategic and International Studies (CSIS). Then, between 2009 and now, it conducted 58 missile tests and four nuclear tests.

“The purpose is to communicate to the US and the world that they don’t just have nuclear capability, but they have a ‘survivable’ nuclear capability,” says Victor Cha, the lead Korea expert at the CSIS.

A country can develop nuclear weapons against, say, the US. But if it can only launch those weapons from fixed sites and it needs liquid fuel to power the rockets, the US can see from space when it is erecting the missile and when it is being fueled. The US can then take the weapon out with a long-range precision missile.

“You could try to pre-empt, but there’s always a danger that you would miss one or two nuclear missiles.”

So the next stage in the evolution of a nuclear weapons state is to develop missiles that can be launched from submarines or mobile launchpads. Better still, if the country can use solid-fuel, the rockets won’t need fueling in advance and thus there will be no lead time to launch the missile. This makes it very hard for the US or its allies to carry out a pre-emptive strike. Thus, the country will have developed a survivable nuclear capability.

“Once North Korea reaches that capability, they will feel like they don’t have to answer to anybody. You could try to pre-empt, but there’s always a danger that you would miss one or two nuclear missiles,” says Cha.

If we take North Korea’s official statement on the fifth nuclear test at face value, the country is giving hints about acquiring such capability or getting close. It reads, “The nuclear test finally examined … nuclear warhead that has been standardized to… be mounted on strategic ballistic rockets.”

It’s China’s game

The sanctions against North Korea haven’t worked, and we know why. “North Korea lives in the space created by geostrategic distrust between China and the United States,” writes Scott Snyder, senior fellow for Korea studies at the Council on Foreign Relations.

China provides up to 90% of North Korea’s trade. “Trade is booming and is now back to pre-sanction levels,” according to a recent investigation by the ABC. “It is easy to see how that is possible. Security along the 1400-km border is minimal.”

“Trade is booming and is now back to pre-sanction levels.”

The US policy on the Korean peninsula is clear. It supports the reunification of the peninsula, led by South Korea. But, as North Korea’s military power grows, the chances of a peaceful reunification, which would involve the dismantling of Kim Jong-un’s regime and denuclearization, become slimmer.

This is not a scenario China would like to support. In the short term, it wouldn’t want to share a border with a country that will face a humanitarian crisis following the fall of the regime. In the long term, China wouldn’t want to see a strong US military presence on its border.

“The UN may call for new sanctions, but unless the Chinese cut off airspace and ports, close the border, stop the North Koreans from using the Chinese financial system… the sanctions aren’t going to work” says Cha.

Show me the money

Even if China were convinced to levy stricter sanctions against North Korea, it’s hard to see how that’s going to crush the rogue regime’s ambitions. The pace of progress suggests that North Korea will soon reach a point where it’s able to sell nuclear weapons to the highest bidder.

“As they’ve done with past missiles, there’s a very good chance they’ll start selling,” says Cha. He’s referring to Pakistan’s Ghauri missiles and Iran’s Shahbad missiles, which are both based on North Korea’s missiles.

The powers that keep North Korea in check aren’t working. Kim Jong-un sees two lame-duck presidents: one in the US and one in South Korea, both of whom will be replaced next year.

Snyder thinks we’ve reached the point where the US and its allies have only two options: either support regime change in North Korea, or, if regime change is not possible, accept that North Korea is a nuclear weapons state. The first option, he says, will need military action and the second will need arming South Korea with nuclear weapons to keep North Korea in check.