Quick answer: In 2017, North Korea’s missile tests and its sixth nuclear test, which it claimed was a hydrogen bomb, led to fierce threats between Pyongyang and Washington and widespread talk of a “new world war”. No war broke out. The crisis turned into talks in 2018, but North Korea kept its weapons, and in June 2026 the Stockholm International Peace Research Institute (SIPRI) estimated that it had possibly assembled around 60 nuclear warheads.
About this article
This article was first published in 2017, at the height of the crisis between the United States and North Korea, when many people feared that a third world war was about to begin. We have kept it as a record of those fears, corrected what the original got wrong, and added what actually happened. Details were checked in October 2026.
Why 2017 felt like the start of a new war
The original article described a world already uneasy after the war in Syria and Donald Trump’s arrival as US President in January 2017, and reported that North Korea was testing new missiles, some of which failed. That was accurate. According to the Arms Control Association’s chronology of US–North Korean nuclear and missile diplomacy:
- Early 2017: North Korea tested the new Pukguksong-2 missile in February and fired four ballistic missiles towards Japan in March. A missile launched on 16 April 2017 exploded shortly after launch.
- July 2017: North Korea tested the Hwasong-14 twice. US, Japanese and South Korean analysts assessed it as an intercontinental ballistic missile (ICBM), a missile with the range to reach the US mainland.
- August 2017: President Trump warned that further threats would be “met with fire and fury like the world has never seen”. North Korea answered with a plan to fire missiles into the waters near the US Pacific territory of Guam, and later flew a Hwasong-12 missile over Japan.
- November 2017: North Korea launched another ICBM on 29 November, which flew for about 53 minutes before landing in the Sea of Japan.
The two countries’ hostility did not start with Syria, as the original article suggested. It goes back to the Korean War (1950–53), which ended in an armistice rather than a peace treaty.
The hydrogen bomb claim
A hydrogen bomb (H-bomb), or thermonuclear weapon, uses a first-stage fission explosion to trigger nuclear fusion, which can release far more energy than the fission bombs dropped on Hiroshima and Nagasaki in 1945.
North Korea first claimed to have tested a hydrogen bomb in its fourth nuclear test on 6 January 2016, though experts doubted the claim because the seismic signal was small. On 2 September 2017, its state media released photos of Kim Jong Un with what it said was a thermonuclear warhead small enough to fit on an ICBM. The next day, 3 September 2017, it carried out its sixth and largest nuclear test and called it a “perfect success”.
The Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) recorded the test as a seismic event of about magnitude 6.1 (revised from an initial 5.8). Many experts estimated the yield at more than 100 kilotons of TNT, far larger than North Korea’s earlier tests. The Arms Control Association notes that the hydrogen bomb claim could not be independently confirmed, although the higher yield was consistent with a boosted fission or thermonuclear device.
What NATO actually said
The original article said a “report from NATO” revealed that North Korea was building hydrogen bombs and trying to sell them. We could not find such a report. What the North Atlantic Treaty Organization (NATO) did publish was a statement by the North Atlantic Council on 6 September 2017. It condemned the 3 September test as a flagrant violation of United Nations Security Council resolutions and a threat to international peace, and called on North Korea to abandon its nuclear and ballistic missile programmes in a complete, verifiable and irreversible way. We have removed the claim about North Korea trying to sell the bomb because we found no NATO source for it. You can read NATO’s own statements on its NATO website.
The world’s response
- United Nations sanctions: on 11 September 2017, the UN Security Council passed Resolution 2375, which banned North Korea’s textile exports and capped its imports of refined petroleum products. Resolution 2397 followed on 22 December 2017 after the November ICBM test, cutting refined petroleum imports by nearly 90 percent.
- War of words: in his first speech to the UN General Assembly on 19 September 2017, Trump threatened to “totally destroy North Korea” if the US had to defend itself or its allies. Kim Jong Un replied with a rare personal statement promising the “highest level of hardline countermeasure in history”.
- Shows of force: US B-1B bombers flew near North Korea’s coast on 23 September 2017, and North Korea’s foreign minister said Trump’s words amounted to a declaration of war.
The original article said North Korea had “clearly” decided to declare war on the United States. North Korea’s statements were extremely hostile, but it did not declare or start a war, and neither did the United States.
What happened next
- 2018: after North Korea took part in the Winter Olympics in South Korea, Kim Jong Un announced on 20 April 2018 that he would suspend nuclear and long-range missile tests and close the Punggye-ri test site. He met South Korea’s President Moon Jae-in on 27 April, and on 12 June 2018 he and Trump held the first summit between a sitting US president and a North Korean leader, in Singapore.
- 2019: a second summit in Hanoi in February ended without agreement, and later talks stalled.
- 2025–26: SIPRI’s Yearbook 2026, released on 8 June 2026, estimated that North Korea had possibly assembled around 60 warheads and had enough fissile material for at least 30 more. It said North Korea continued to unveil and test new missiles in 2025, including the solid-fuelled Hwasong-20 ICBM, and aims to expand its arsenal “exponentially”.
As of our October 2026 check, the September 2017 explosion remained North Korea’s most recent reported nuclear test.
Why a war between nuclear powers would be so dangerous
The original article closed by warning that a war between heavily armed countries would be destructive for everyone. That remains true. SIPRI estimated a world total of 12,187 nuclear warheads in January 2026, about 9,745 of them in military stockpiles for potential use. The 2017 crisis is also a reminder that frightening headlines and “World War III” predictions do not always come true: for all the threats exchanged that year, the two sides eventually sat down to talk. For reliable updates on international tensions, follow established news organisations and official statements rather than viral predictions.
Other articles from the same 2017 moment cover the World War III prediction that failed, earlier crises and close calls since 1945 and what a nuclear war would really leave behind.
Frequently asked questions
Did North Korea really test a hydrogen bomb in 2017?
North Korea said its 3 September 2017 test was a hydrogen bomb. The claim has not been independently confirmed, but the test was its largest ever, with an estimated yield above 100 kilotons, which experts said was consistent with a boosted fission or thermonuclear device.
Did the 2017 crisis start a world war?
No. Despite missile tests, a nuclear test and harsh threats on both sides, no war broke out. The crisis led to summits in 2018 and 2019.
How many nuclear weapons does North Korea have?
Nobody outside North Korea knows exactly. SIPRI’s June 2026 estimate is that it had possibly assembled around 60 warheads, with fissile material for at least 30 more.
What sanctions did the UN impose after the 2017 nuclear test?
Security Council Resolution 2375 (11 September 2017) banned North Korean textile exports and capped refined petroleum imports. Resolution 2397 (22 December 2017) tightened the petroleum limits further and required countries to send North Korean workers home.
This article was updated in October 2026 using the Arms Control Association’s chronology of US–North Korean nuclear and missile diplomacy, the North Atlantic Council’s statement of 6 September 2017, the CTBTO’s seismic data as reported there, and SIPRI Yearbook 2026.
