One objection is Trump will ‘legitimise’ North Korea. However, Washington recognises North Korea as a nation-state. The US has negotiated with Pyongyang over seven decades, from talks at the demilitarised zone to meetings among diplomats in third countries and at the UN, to a visit to Pyongyang by the secretary of state, in 2000, to quasi-diplomatic visits by former US presidents Bill Clinton and Jimmy Carter.

The Kim family, with successions from grandfather to father to son, has ruled the nation from its founding, surviving war, sanctions, famine, natural disasters, and the fall of their patron, the Soviet Union. Kim is worshipped by his own people as a god, while outsiders have long-formed their opinions about him; he has no need for a propaganda coup. America has negotiated with, and even supported, evil dictators before. North Korea is a nuclear power, whether anyone likes that or not. The criteria for ‘legitimacy’ appear long met, with or without Trump.

The US State Department is depleted, say some: The US has no ambassador to South Korea; the special representative for North Korea policy has just retired. But it is disingenuous to claim there is no one left to negotiate with Pyongyang, simply because their names are unfamiliar to journalists.

Marc Knapper, the current charge d’affaires at the US embassy in Seoul, has more than 20 years of Korea experience, including as deputy chief of mission in Seoul. He has been to North Korea multiple times and is trusted by South Korea. His minister-counselor for political affairs, Edwin Sagurton, also has spent years on the peninsula and worked in the North. A third senior American official, Busan consul Dae B Kim, was born in Seoul and has worked on Korean issues for some 20 years.He served alongside Madeleine Albright, during her visit to Pyongyang. All three of the diplomats speak Korean.

In Washington, the retirement of Joe Yun, the special representative, is a loss, but his deputy, Mark Lambert, is acting in his capacity. Lambert has significant Korea knowledge, having negotiated with the North as special envoy for the Six-Party Talks on North Korea’s nuclear programme. There are similar decades of Korean expertise at the National Security Council, the Central Intelligence Agency, in the military, as well as among South Korean diplomats, to support Trump’s efforts. Preparation? These men and women have spent their careers preparing.

Another criticism: It is wrong to start with a summit; Trump already gave away the big prize. This argument was old, back when it was used to criticise Richard Nixon for his ‘opening’ of his China visit in 1972. In the case of North Korea, the idea of holding lower-level talks, leading up to a triumphant meeting between Trump and Kim, is a non-starter. It is Kim who sets the direction for North Korea’s foreign relations, and it is important for him to signal this move forward with his full approval. It is unlikely North Korea’s lower-level functionaries would be allowed to claim small victories on Kim’s behalf, without his ceremonial leadership demonstrated. Previous US presidents have held off a summit, pending progress, the result being that there was no progress over successive administrations. North Korea is a top-down system (some say the same for Trump’s Washington), and needs to be dealt with as such.

The other reason to begin with a summit is there is little of the connective tissue of diplomacy between Washington and North Korea, the important mid-level contacts and relationships which could smooth over the logistics and details of preparation.

Both sides can also use the optics of a summit to empower diplomats, such as the often embattled US secretary of state, Rex Tillerson.

A final criticism is that the North Koreans aren’t serious about negotiations. Yet the North showed its seriousness by sending Kim’s sister, Kim Yo Jong (a sign of Kim’s approval) and 90-year-old Kim Yong Nam (a sign of the inner circle’s approval) to last month’s Winter Olympics in the South. Kim Yong Nam has served all three North Korean rulers, was formerly minister of foreign affairs, and, as a veteran of the 1950s war, has unimpeachable credibility with the military. The US has carefully kept him off any sanctions list, ostensibly because he is not directly involved in nuclear development, meaning he is free to travel to Washington. He will be a key player.

So, what happens next? First, it’s going to take time and trust. Kim Jong Un, and perhaps Trump, too, will need to balance conciliatory steps forward with bellicose gestures directed at a limited, but important, domestic hardline audience. So, there will likely be tweets, and setbacks.

If the two leaders meet, expect simple things to begin: sports and academic exchanges; the return of one or more of the three Americans in jail in North Korea; an invitation to search for the remains of any Americans or South Koreans killed north of the 38th parallel in the Korean War. Pyongyang may extend its self-imposed moratorium on nuclear testing, while Washington agrees to limited changes in scheduled military exercises.

Such small-scale wins build trust. That can lead to the kind of Cold War-style negotiations that eventually saw the US and Soviet Union pull classes of weapons out of service to ratchet down tensions. It is foolish and ahistorical to imagine the Trump-Kim summit itself will lead anywhere near denuclearisation.

Washington should continue to let the South Koreans lead, as they have in delivering Kim’s offer to meet Trump. The White House was tactically adept in allowing the announcement of Trump’s acceptance to be made by South Korean officials.

Ultimate peace will be made by the Koreas, who, after all, have most at stake. Leaders on both sides include survivors of the Korean War. They retain strong emotional ties, based on the Korean sense of ‘wuli’ — us versus them — with ‘us’ being the Korean people as a whole. They are facing their own mortality, and are aware of their legacies. This is their generation’s now, to win or lose. Negotiations are not always an even give-and-take, and that is not a sign of weakness, but of strength and skill. Success on the Korean peninsula, as in the Cold War, will be measured by the continued absence of war and the continued sense war is increasingly unlikely.

Those who criticise Trump’s plans to meet with Kim, and who will pick at the edges of any progress, should remember that diplomacy, the alternative to war, means the messy business of meeting your adversaries, not ignoring them.

Peter Van Buren, a 24-year State Department veteran, is the author of We Meant Well: How I Helped Lose the Battle for the Hearts and Minds of the Iraqi People and Hooper’s War: A Novel of WWII Japan. @WeMeantWell