After more than a year of belligerent rhetoric, missile tests and nuclear explosions, North Korea and the US have agreed to talk to each other directly.

This dramatic development is the first time that the US has agreed to meet with the North Koreans without any preconditions.

Why has this happened so suddenly?

The change in US policy appears to be a direct response to South Korean president Moon Jae-in’s policy of rapprochement with the north.

After Pyongyang sent a delegation to the 2018 Winter Olympics in and the two Koreas fielded a joint team, it was announced by negotiators from Seoul that the North Koreans were willing to open a dialogue with the US. Then, on March 6, the South Koreans announced that the North was willing to discuss giving up its nuclear weapons. Perhaps to avoid a rift with the South – a close US ally which would bear the brunt of any war with the north – Washington began to reconsider its position.

What is the US’s new policy?

Until a few weeks ago, the US’s stance was that North Korea would have to take demonstrable steps to denuclearise before the negotiations could begin, even at a low level – in other words, it would have to give up its chief leverage over the US before the two countries could talk directly at all.

However, the US vice-president, Mike Pence, recently announced a new US policy, more in line with the current South Korean position: “At the outset of any new dialogue or negotiations,” he said, North Korea would have to “put denuclearisation on the table and take concrete steps with the world community to dismantle, permanently and irreversibly, their nuclear and ballistic missile programs.”

The message seems to be that Pyongyang only has to agree to discuss denuclearisation, not to actually begin disarming in advance of talks.

What does North Korea want?

North Korea’s goals have been fairly predictable and consistent since the nuclear stand-off began in the early 1990s. The regime in Pyongyang is morally repugnant and superficially often bizarre, but its fear of becoming a US military target is not without grounds.

The US carries out extensive military exercises on and around the Korean Peninsula, and also has 11 military bases and 28,500 troops in South Korea – a hangover from from the 1950-53 war. In fact, Washington and Pyongyang are still technically at war with each other – a 1953 ceasefire agreement has frozen the conflict for 65 years, but a formal end to the war and the normalisation of relations between the two countries remains the ultimate objective for Pyongyang. The Kim regime therefore sees its nuclear weapons as the ultimate guarantee of security against a superpower that it still considers a direct threat.

What are the best and worst outcomes?

The best outcome would be that Trump uses his purported deal-making skills to agree to a peace treaty with North Korea, a deal that denuclearises the Korean Peninsula, scales back the US military presence there and institutes normal diplomatic relations with Pyongyang. The question is whether Trump has the diplomatic skill to do this.

The South Koreans have demonstrated that it’s possible to negotiate with the North and come to a mutual understanding. But Trump has very little diplomatic experience of any kind, especially when it comes to sensitive high-stakes negotiations. He is egotistic and often lashes out before thinking. These talks represent a precious and rare opportunity, but Trump is not the person most observers would want to see in the driving seat.

What happened last time the US and North Korea had productive talks?

The closest the two sides came to solving the problem was the 1994 Agreed Framework, signed by the Clinton administration and Kim Jong-in’s grandfather, Kim Il-sung. Under the terms of that agreement, North Korea agreed to freeze and ultimately dismantle its nuclear programme in exchange for “the full normalisation of political and economic relations with the US”.

For a while, things seemed to go well – but by 1998, it was clear that the US was not living up to its side of the bargain. Little was done to normalise diplomatic relations. The hawkish Republican Congress, which was opposed to the agreement, consistently refused to fund the light-water nuclear reactors the North Koreans had been promised, and heavy fuel shipments – also part of the agreement – were usually delivered late.

If Trump strikes some sort of deal with Kim, selling it to the Republicans in Congress will be a tall order. Given Trump’s poor record of passing major legislation of any kind, there is little to suggest he would be capable of doing this. That said, things might be very different if the Democrats take control of all or part of Congress in the November 2018 elections.

Is unpredictability a good strategy, or a dangerous one?

Ambiguity and unpredictability are far from ideal in any scenario, especially one where nuclear weapons are involved. If the US’s policy is too unclear or inconsistent, adversaries may miscalculate – and the possibility of accidental nuclear war on the Korean Peninsula cannot be ruled out entirely.

US policy has often been inconsistent and unclear over the past year. Trump’s bellicose rhetoric and insistence that the US military explore multiple options for the deployment of force, including pre-emptive nuclear strikes, may well give the impression that the administration is actually considering such a strike. On the other hand, Trump’s threats have often been undermined by members of his own cabinet who have affirmed that diplomacy is the first choice. The most senior US military official, General Joseph Durnford, went so far as to say military action against North Korea would be “catastrophic”.

Who speaks for the US? Who should the North Koreans listen to? It’s not always easy to tell. Now that Trump has accepted this invitation to talk, he must remain consistent in his willingness to negotiate.