With the window closing fast for the US to stop Kim Jong-un from obtaining a nuclear-tipped intercontinental ballistic missile, North Korea watchers are starting to analyse President Donald Trump’s military options. He warned on Tuesday that North Korea would be met with “fire and fury” if it continues to make threats. After the United Nations agreed to its most stringent sanctions yet on Kim’s regime, North Korea repeated its stance that its nuclear weapons programme is necessary to deter a US invasion. For Trump and the US, there are no easy choices.

1. Can’t the US try a surgical strike?

It probably wouldn’t work well enough. North Korea’s missiles and nuclear facilities are dispersed and hidden throughout the country’s mountainous terrain. Failing to hit them all would leave some 10 million people in Seoul, 38 million people in the Tokyo vicinity and tens of thousands of US military personnel in northeast Asia vulnerable to missile attacks — with either conventional or nuclear warheads. Even if the US managed to wipe out everything, Seoul would still be vulnerable to attacks from North Korea’s artillery.

2. Why might Kim go nuclear?

“Even a limited strike“ by the US “would run the risk of being understood by the North Koreans to be the beginning of a much larger strike, and they might choose to use their nuclear weapons,” said Jeffrey Lewis, director of the East Asia nonproliferation programme at the Middlebury Institute of International Studies. Somehow, the US would need to signal to both North Korea and China — Pyongyang’s main ally and trading partner — that a surgical military strike is limited, and that they should avoid nuclear retaliation.

3. Is regime change an option?

New leadership wouldn’t necessarily lead to a new way of thinking among North Korea’s leadership. Kim’s prolonged exposure to Western values while at school in Switzerland led some to speculate that he might opt to open his country to the world — until he took power and proved them wrong. Moreover, if Kim somehow were targeted for removal, the ruling clique surrounding him would have to go as well — making for a very long kill list. China, fearing both a refugee crisis and US troops on its border, would likely seek to prop up the existing regime.

4. Does that mean all-out war is the best US option?

A full-scale invasion would be necessary to quickly take out North Korea’s artillery as well as its missile and nuclear programmes. Yet any sign of an imminent strike — such as a buildup of US firepower, mobilisation of South Korean and Japanese militaries and the evacuation of American citizens in the region — could prompt North Korea to strike preemptively. China and Russia may also be sucked in. “Realistically, war has to be avoided,” said John Delury, an assistant professor of international studies at Yonsei University in South Korea. “When you run any cost-benefit analysis, it’s insanity.”

5. How might North Korea retaliate?

The most immediate reaction would likely be massive artillery fire on Seoul and its surroundings. North Korean artillery installations along the border can be activated faster than air or naval assets and larger ballistic missiles that can target South Korean, Japanese or American bases in the region with nuclear, chemical and biological weapons. Those countries have ballistic-missile-defence systems in place but can’t guarantee they will shoot down everything. Japan has begun offering advice to its citizens on what to do in the event a missile lands near them — essentially try to get under ground — and US firms are marketing missile shelters. While it’s unclear if North Korea can successfully target US cities like Denver and Chicago with a nuclear ICBM, it’s similarly unknown if US defence systems can strike it down — adding to American anxieties.

6. What would be the economic toll if war broke out?

South Korea accounts for about 1.9 percent of the world’s economy and is home to companies including Samsung Electronics and Hyundai. A severe drop in business activity due to war on the peninsula would cause widespread pain in the region and globally — and that’s without deployment of North Korea’s nuclear weapons against its neighbour. Global financial markets would also suffer a tremendous shock in the short term, with flight to safe haven assets such as gold, the US dollar and the Swiss franc. “The humanitarian crisis and economic reconstruction of the Korean peninsula after such a nuclear conflict would require large-scale international co-operation led by China, the US and the European Union and it would likely take over a decade to rebuild the economy,” according to Rajiv Biswas, chief Asia-Pacific economist for IHS Markit.

In pictures: North Korea military drill Show all 8 1 /8 In pictures: North Korea military drill In pictures: North Korea military drill North Korea's leader Kim Jong Un watches a military drill marking the 85th anniversary of the establishment of the Korean People's Army (KPA) KCNA/Handout via REUTERS In pictures: North Korea military drill A military drill marking the 85th anniversary of the establishment of the Korean People's Army (KPA) is seen in this handout photo by North Korea's Korean Central News Agency (KCNA) KCNA/Handout via REUTERS In pictures: North Korea military drill A military drill marking the 85th anniversary of the establishment of the Korean People's Army (KPA) is seen in this handout photo by North Korea's Korean Central News Agency (KCNA) KCNA/Handout via REUTERS In pictures: North Korea military drill A military drill marking the 85th anniversary of the establishment of the Korean People's Army (KPA) KCNA/Handout via REUTERS In pictures: North Korea military drill A military drill marking the 85th anniversary of the establishment of the Korean People's Army (KPA) KCNA/Handout via REUTERS In pictures: North Korea military drill This image made from video of still images broadcast in a news bulletin by North Korea's KRT, shows what was said to be a 'Combined Fire Demonstration' held to celebrate the 85th anniversary of the North Korean army, in Wonsan, North Korea. KRT via AP Video In pictures: North Korea military drill This image made from video of still images broadcast in a news bulletin by North Korea's KRT, shows what was said to be a 'Combined Fire Demonstration' held to celebrate the 85th anniversary of the North Korean army, in Wonsan, North Korea. KRT via AP Video In pictures: North Korea military drill This image made from video of still images broadcast in a news bulletin by North Korea's KRT, shows what was said to be a 'Combined Fire Demonstration' held to celebrate the 85th anniversary of the North Korean army, in Wonsan, North Korea. KRT via AP Video

7. What options remain on the table?

Many analysts say it’s time to start talks to prevent the situation from worsening. Stopping North Korea from obtaining a thermonuclear weapon, or more advanced solid-fuel missiles, is a goal worth pursuing, according to Lewis. However unpalatable it may seem, that means offering rewards to entice North Korea back to the negotiating table. Lewis suggested one reward could be to scale back US-led military drills around North Korea. The question of what can be offered to the North Koreans “is a conversation that should be happening both with the public, with Congress and with the North Koreans, instead of having this imaginary conversation about war scenarios,” said Delury. “The realistic option is a diplomatic one that slows this thing down. And that’s going to require a lot of talks.”