US President Donald Trump and North Korean Supreme Leader Kim Jong-un emerged from the much-anticipated summit on Tuesday to sign an agreement establishing a new era in bilateral relations. Key among the measures agreed is a commitment to Pyongyang “working toward the complete denuclearisation” of the Korean peninsula , offering the clear potential for Trump’s first major foreign policy win. Much ambiguity remains in the text signed in Singapore , and any final, comprehensive deal between Washington and Pyongyang is months, if not years, away. Yet, it is clear that it would be a remarkable achievement if Trump were to help preside over verifiable and comprehensive denuclearisation, while also “building a stable and lasting peace regime on the continent”. This would involve sealing a treaty between North and South Korea to supplement the armistice ending the 1950-53 Korean war, and in the process deescalating tensions in the world’s last cold-war-era frontier. Should Kim ultimately decide to stick to the spirit of Tuesday’s agreement and abandon North Korea’s nuclear programme in exchange for US economic aid and security guarantees, this would – potentially – be central to Trump’s foreign policy legacy. The reason is that, almost 18 months into office, Trump’s international actions have been defined mainly by the dismantling of policies of previous presidents, especially Barack Obama , rather than building something new. He has, for instance, recently withdrawn United States participation in the Iran nuclear agreement. Before that decision, he scrapped US involvement in the Trans-Pacific Partnership (TPP) trade deal with key allies in Asia-Pacific and the Americas; withdrew Washington from the Paris climate change deal agreed by over 170 nations; and, launched a review of the North America Free Trade Agreement which may yet collapse in 2018. The Iran, TPP and Paris initiatives were Obama-era signature policies, and Trump has also partially rolled back other key measures from the previous administration, including the Cuba liberalisation policy. Watch: The historic moment Donald Trump and Kim Jong-un met Trump’s foreign policy wins will be his ticket to re-election success at home Yet, for all this diplomatic action, the new administration has failed to forge any clear, coherent and comprehensive new Trump doctrine centred around his “America first” vision. When Trump moved into the White House, he promised a platform that could have reshaped US foreign and trade policy more radically than at any point since the beginning of the cold war – when then-president Harry Truman helped build a consensus around US global leadership. To be sure, Trump has made some moves to shift away from this post-war orthodoxy – pursued by both Democratic and Republican presidents – such as building US-led alliances to expand the liberal democratic order . But, in practice, much of the past 18 months has also been characterised by policy incoherence and U-turns on issues such as military action in 2017 and 2018 in Syria – a departure from Trump’s 2016 campaign rhetoric; and whether key international alliances like Nato are “ obsolete ” or “not obsolete”. Donald Trump is alienating allies the US needs to confront China on trade, panel warns These flip-flops reflect not just the ad hoc nature of the president’s style of governing, and his contrarian character, but also the divisions within his team on key foreign policy issues. Take the example of the Paris climate deal, Iran nuclear agreement and TPP, where then-secretary of state Rex Tillerson was just one of the senior members of his team urging Trump to remain in the accords. Yet, Trump now appears to have in place a foreign policy personnel much more aligned to his political instincts. Former CIA director Mike Pompeo has replaced Tillerson as secretary of state, and the conservative hawk John Bolton has taken over as national security adviser from the more pragmatic General H.R. McMaster. This changing of the guard could be very important to Trump in that his political window of opportunity to put an enduring stamp on US foreign policy may soon narrow rapidly – unless he wins a second term in 2020. Damaging actions by Trump on Iran deal must be fully resisted With this in mind, he and his new team will now seek to double down on other foreign policy priorities, including the ambition to do the “deal of the century” in the Middle East with Israel and the Palestinians (although this will become more complicated by his decision to move the US embassy to Jerusalem ); and forge renegotiated economic relationships with key countries like Japan and China , seen by Trump as less one-sided and detrimental to the US. 10 things you need to know about the Trump-Kim summit in Singapore It is also to be hoped that Trump’s new team will prove better foils than Tillerson and McMaster were for the president’s ad hoc style of governing, which regularly exposes a lack of experience and knowledge of international issues. If so, this will help serve as a compass for the White House in navigating the uncertainties of international affairs. Taken overall, the historic opportunity offered by the Singapore summit could become a central part of Trump’s foreign policy legacy. However, in this high-stakes gamble for glory, he could still end up emulating many others who have failed to bring a sustained, peaceful diplomatic outcome to one of the key international challenges facing the US. Andrew Hammond is an associate at LSE IDEAS at the London School of Economics