There is room for concern in tripartite negotiations as complex as those about to commence in Singapore between the United States, North Korea, and South Korea. But there is also cause for optimism—Kim Jong-un reportedly fired top military leaders who may have dissented over his approaches to South Korea and the United States. And the three nations’ leaders have never before sat down together to work out issues. So this is all new.

And when all is over, there’s no basis for saying anything short of a full denuclearization deal means Donald Trump—or South Korean president Moon Jae-in for that matter—has failed. Diplomacy simply does not work that way.

One of the more balanced views of the Singapore summit comes from former State Department North Korea expert Joseph Yun. Yun’s February retirement as special representative for North Korea Policy triggered a round of dire statements that his absence left a “void at head of Trump’s Korea diplomacy.” Similar end-of-the-world predictions were made over the lack of an American ambassador in Seoul. The Council on Foreign Relations then assessed the chances of war on the Korean Peninsula at 50 percent.

Ambassador Yun himself is much more of a realist than most others who have commented on the Peninsula. Writing in Foreign Affairs, he dismissed quickly those expecting some sort of complete denuclearization deal to transpire over the next week. Instead, he suggests that “success” will include reinforcing North Korea’s self-imposed moratoriums on nuclear and missile tests, and opening the Yongbyon nuclear facilities to the International Atomic Energy Agency. The North will also need to provide a full list of its nuclear sites and an accounting of its fissile material.

But even Joe Yun falls victim to unrealistic expectations when he says success will include at least a timeline for full denuclearization and the elimination of North Korea’s intercontinental ballistic missiles, all by 2020, in order to silence skeptics. Yun was involved in Madeleine Albright’s visit to Pyongyang in 2000 before North Korea even had nuclear weapons, and wouldn’t have been caught dead suggesting such unrealistic criteria then: the modest hope 18 years ago was for follow-on meetings leading someday to a presidential summit. Ironically, then-president Bill Clinton held off pending more interim progress, the result being that no real advances occurred during successive administrations. It took Moon Jae-in to convince Washington that North Korea is a uniquely top-down system and needs to be dealt with as such.

Managing expectations, for the public and at the negotiating table, is key. History provides examples the principals in Singapore should be reviewing. Though imperfect, the 2015 accord with Iran is a workable model. It focused on specific actions, independently verifiable by the International Atomic Energy Agency. For example, Iran reduced its uranium stockpile to 300 kilograms at an enrichment level of 3.67 percent. The other parties to the accord, especially the United States, were equally committed to specific actions over a timeline that extended decades. Nobody hoped peace would simply break out. Denuclearization is far more complicated than offering sanctions relief over tea in return for boxing up the bad bombs.

Deeper history offers the painstakingly complex Cold War nuclear treaties with the USSR, where success was measured by the continued absence of war and the continued sense that war was increasingly unlikely. In contrast, look at the example of Libya (ridiculously cited in the positive by National Security Advisor John Bolton and Vice President Mike Pence), under which Moammar Gaddafi gave up a limited nuclear development program under threat only for the U.S. to renege on its word; we are still watching the chaos in northern Africa unfold as to how that worked out.

Success is in the long game, not in facile predictions of failure. William Johnson, a retired Foreign Service Officer who served as the State Department’s political advisor on special operations to the United States’ Pacific Command, explained:

If “failed” negotiations obviated further diplomatic options, Trump would need no ambassadors, and no advice from anyone on how to conduct diplomatic affairs. For we have failed on multiple occasions. But diplomacy is often a series of failures, and in the best case, the failures become incrementally less bad, until the least spectacular failure is declared to be success. Diplomacy is a game where the goalposts are supposed to move, and often, to move erratically. Trump needs a plan, with specific goals, each laid out neatly in a set of talking points, not because he will attain those goals, but because he needs to figure out how short of them he can afford to fall or how far beyond them he can push his interlocutor.

A process, not an event.

Success in Singapore may include an agreement to formally end the Korean War (supported by some 80 percent of South Koreans—this would be a massive domestic win for Moon, himself the son of North Korean refugees, ahead of the June 13 South Korean by-elections). Success may also include humanitarian aid from the South, perhaps some modest investments from China, and the scaled easing of sanctions from the American side. These are not concessions, but the give and take of negotiations, the stuff of diplomacy, where uneven forward movement can be a sign of strength and strategy. Success might be Kim formalizing the promises he has already voiced in his Panmunjom meetings with his South Korean counterpart. Success could also be keeping Moon Jae-in in the center of unfolding events: no other nuclear negotiations in history have had such an interlocutor, one who shares goals near equally with both other parties, and who can talk to each as a partner.

If people demand that Trump bull into the room and say “Nukes, number one and we’re done,” the process will indeed fail. Wipe clean the cartoon image of Kim as a madman. North Korea currently has nuclear weapons as the guarantor of its survival; that is a starting point, not a debatable one. If the United States and South Korea want the North to give up those weapons, something has to replace them as that assurance of survival. The ask here is extraordinary—only one nation in history that self-developed nuclear weapons, South Africa, has ever given them up, and that was because their purpose, the survival of the white apartheid regime, disappeared into history.

Success in Singapore will be an agreement to meet again, and again after that. It should not be forgotten that the more modest 2015 Iranian Accord took 20 months to negotiate. Success means forwarding the process of building trust and creating an infrastructure to solve the inevitable problems (sadly, yes, there will likely be tweets) that accompany the often herky-jerky path forward. Anyone demanding more than that from the June 12 meeting wants it to fail.

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. Follow him on Twitter @WeMeantWell.