So Rex Tillerson is gone. Yet amid the flurry of speculation and debate prompted by his departure, we shouldn’t lose sight of the fact that President Trump has already committed himself to talks with North Korean leader Kim Jong Un. Trump now has to prepare for the biggest negotiation of his life — even if he doesn’t have his new chief diplomat in place to help.

The fact remains that Trump made the right decision to pursue diplomacy rather than war to achieve nuclear disarmament in North Korea. His previous strategy of a “bloody nose” military conflict with the North offered little chance of achieving denuclearization and also risked pulling the United States into a major war on the Korean Peninsula. When compared with this dangerous alternative, Trump’s policy pivot must be welcomed.

It remains unclear, however, if Trump has developed the sophisticated, multipronged, comprehensive strategy needed to compel North Korean leader Kim Jong Un to give up forever his nuclear weapons. Trump has already made several initial negotiating mistakes. Going forward, he will need to show greater care in articulating and then implementing a winning diplomatic strategy. Diplomacy is hard work — and nuclear diplomacy with North Korea especially so.

Trump’s first negotiating mistake was giving away for free something highly desired by Kim: a presidential meeting. Before agreeing to a head-of-state summit, Trump could have demanded, for example, that Kim state on the record that he was ready to pursue denuclearization. Achieving that objective, after all, is the only reason for a summit. Unfortunately, our only source for knowing whether Kim is ready to pursue this goal is a verbal message from South Korea’s national security adviser.

Trump’s second mistake was not securing interagency support for his gambit beforehand. Divided administrations weaken presidential diplomacy. There is nothing worse than a defense secretary or national security adviser whispering to the press, “I told you so,” when the negotiations do not unfold according to plan.

Trump’s third mistake was to make this negotiation a bilateral affair. In negotiating the Iranian nuclear deal, American diplomats benefited from having other countries, especially Russia, involved in the process. When talking with North Korea, it would be useful to have China at the table.

Trump’s possible fourth mistake was to set a very high bar — permanent denuclearization — as the end goal of his diplomacy. That outcome will be very hard to achieve. By staking out this maximalist objective at the very beginning of negotiations, Trump has tied his own hands, preventing him from settling for interim outcomes that also may serve American national interests. (Of course, if Trump succeeds, then tying his own hands at this early stage in the negotiations will be seen as a stroke of genius.)

Trump’s fifth mistake is to disparage the Iranian nuclear deal as be begins to pursue his nuclear deal with North Korea. If the United States cannot be trusted to honor its commitments to Iran, why should the North Koreans trust us to implement an agreement with them?

Trump’s sixth mistake is to begin these negotiations without a full diplomatic team in place. Diplomacy is a team sport. Even if Trump succeeds in launching a productive process aimed toward North Korean denuclearization, he will need an interagency team of negotiators empowered with presidential authority to follow up with their North Korean interlocutors on the complex details of any future deal.

At the highest levels, Trump’s national security team lacks depth in both diplomacy and North Korea. Whether Mike Pompeo, Trump’s choice to replace Tillerson, can receive confirmation in time for the talks remains to be seen. Even if he’s confirmed, though, the reality is that Pompeo has no diplomatic experience at all.

At lower levels, the Trump administration has yet to name an ambassador in South Korea. The administration has just lost its most experienced North Korean hand at the State Department and has either not named or not  secured Senate confirmation for a new undersecretary of state for political affairs, an undersecretary of state for arms control and international security affairs, or an assistant secretary for arms control, verification and compliance — all positions usually involved in arms control negotiations.

All of the acting diplomats in these positions are first-rate, but they lack the authority to negotiate on behalf of Trump. At the National Security Council, Korea experts celebrate the presence of Allison Hooker as the director responsible for the Korean Peninsula, but conservative media outlets have berated her as an “Obama holdover.” To achieve success, Trump’s team needs to be beefed-up. The president might even consider naming a special envoy — former national security adviser Stephen Hadley or former ambassador Chris Hill — to lead the negotiations.

Trump’s seventh mistake, perhaps better described as a very risky move, was to start these negotiations at the presidential level. Previous presidents have empowered lower-level officials to begin negotiations, sometimes even in secret, in part just to gather intelligence about the other side’s initial positions before getting the commander in chief involved. It may be that Trump’s big-bang approach is needed to jump-start serious talks. But if the presidential summit does not produce a breakthrough, then it will be harder for lower-level official to pick up the pieces.

None of these mistakes is fatal; most can be reversed. But the sheer number of them suggests that Trump needs to up his diplomatic game, learn more about the subject, invest more time into mapping out the multiple stages that will be needed to achieve success, and hire more people to help the cause. Trump has just launched the biggest diplomatic negotiation of his presidency and the biggest dealmaking moment of his life. No less than war and peace hang in the balance. Americans and the world need Trump to overcome his shaky start and succeed.