In November 2025, the United States (US) published its National Security Strategy (NSS), which stated that the Trump administration ‘will reassert and enforce the Monroe Doctrine to restore American pre-eminence in the Western Hemisphere’. This includes protecting the homeland and access to key geographies. The US would ‘deny non-hemispheric competitors the ability to position forces or other threatening capabilities’ and prevent its adversaries from owning or controlling ‘strategically vital assets’.
This was referred to as the ‘Trump corollary’ to the Monroe Doctrine. The Department of War reaffirmed this approach with the National Defence Strategy (NDS), released in January 2026. The NDS asserted that ‘American interests are under threat in the Western Hemisphere’, and that the corollary is a ‘common-sense and potent restoration of American power and prerogatives in this hemisphere, consistent with Americans’ interests.’
Most discussion about the Trump corollary focused first on what it meant for the Western Hemisphere. This, however, misses critical context – the linkage of security and stability in the Western Hemisphere to potential conflict in the Indo-Pacific. For this administration, the two theatres are inextricably linked. Understanding this is vitally important for evaluating what – if anything – the United Kingdom (UK) could or should do in response to the new strategic posture of Donald Trump, President of the US.
Washington’s hemispheric focus
America has long assumed that it held primacy over the Western Hemisphere, but, in practice, it has maintained inconsistent and uneven attention on regional affairs. Instead of sustained engagement and commitment, Washington’s focus was fleeting, and almost exclusively linked to periods of crisis and instability. Domestic political issues, such as immigration and the war on drugs, have driven most engagement in recent years, rather than a concerted policy prioritisation.
In this diplomatic and economic vacuum, the People’s Republic of China (PRC) was able to take advantage, expanding its own reach in and across Latin and South America. The US’ distraction throughout the two decades of the so-called ‘Global War on Terror’ proved to be a boon for Beijing. Through financial largesse accompanied by few (if any) expectations or requirements, the PRC secured access to critical minerals, rich fishing waters, and infrastructure projects which increasingly caused the Western Hemisphere to fall within Beijing’s practical sphere of influence in lieu of the US’ rhetorical remit.
By (re)asserting American interests in the region, the Trump administration hopes to ensure defence and security in its own backyard. By effectively closing the southern border and deploying law and immigration enforcement authorities, the President has succeeded in largely halting illegal immigration. The US has also taken the fight against drug traffickers to waters off the coast of South America, striking suspected narco-vessels. This is only part of the administration’s calculus.
If the Trump administration can increase its access to regional energy assets, such as in Venezuela – offsetting the depletion in the US’ strategic oil reserves – and critical minerals and rare earth elements (which are overwhelmingly controlled by the PRC), Washington will in turn reduce its exposure to hydrocarbon market instability from the Persian Gulf and on supply chains controlled by Beijing. Done successfully, this could decrease the need for future American interventions in the Middle East, and ensure that the US can better weather the potential impact of a conflict in the Indo-Pacific over Taiwan on the American economy, thereby allowing it to intervene with less strategic risk. This is now, of course, complicated by the secondary effects of Operation EPIC FURY against Iran.
The US also aims to secure strategic geographic territory in the region by denying it to the PRC and, to a lesser degree, Russia. The Panama Canal is the central transportation linkage between the Atlantic and Pacific oceans. The possibility that Beijing could directly or indirectly control the canal or its operation is an unacceptable risk for Washington.
The Euro-Atlantic theatre
The diplomatic furore that resulted from Trump’s attempt to secure Greenland masked its strategic relevance. Greenland is vitally important for controlling access from the Arctic into the North Atlantic – the Greenland-Iceland-UK (GIUK) gap. Control of these waters allows the North Atlantic Treaty Organisation (NATO) to monitor and track Russian submarines, as well as containing the Kremlin’s strategic assets from departing their Arctic bastion. Greenland is also vital real estate for the missile defence architecture of the US homeland, hence Trump’s firm stance on his desire for sovereign control of the island to hedge against losing access in the future.
Given these considerations, the first policy priority for the UK is to ‘keep calm and carry on’. The doctrine, such as it is, does not target Britain or its immediate interests. If anything, the Trump administration has worked to ensure His Majesty’s (HM) Government’s seat at the table. The UK’s presence at the convening of the Western Hemisphere’s defence chiefs reflected a recognition by America of Britain’s interests in the region.
This is unlikely to change. The UK has personnel embedded in the Joint Inter-Agency Task Force South, working daily with the US on counter-narcotics operations in the Western Hemisphere, and this continues as business as usual.
Given the threat picture in Latin and South America, the requirements for presence there are well below what would be comparably necessary in the Euro-Atlantic, or indeed the Gulf region.
The likelihood that significant friction or policy conflict will result between Washington and London in the region is limited. There is certainly room for conflict over specific elements of the policy as it is applied, as evidenced by the temporary suspension of intelligence from British sources in the targeting of narco-traffickers in the Caribbean. Indeed, HM Government’s focus on the rule of international law could set up further conflicts of a similar vein (such as was the case over Iran). This is, of course, an issue for Sir Keir Starmer, Prime Minister, and not Trump, who has demonstrated little (if any) interest in international law – a position that is unlikely to change.
The military buildup of naval and military assets ahead of the operation in Venezuela notwithstanding, the impact of American force deployment in the Western Hemisphere on broader global engagements is likely limited, at least in the near term. The issue is not so much power projection against Latin and South American countries, but rather the assertion of the US’ interests through measured presence and deployment, and periodic joint exercises and training with partner militaries.
In terms of force deployments, the Trump administration’s likely calculus is based on a greater assumption of responsibility for the NATO defence and deterrence mission by the European members of the alliance, which necessitates reduced American presence in the Euro-Atlantic. This enables the belated rebalance to the Indo-Pacific. Given the threat picture in Latin and South America, the requirements for presence there are well below what would be comparably necessary in the Euro-Atlantic, or indeed the Gulf region.
The frictions resulting from the Prime Minister’s initial decision to deny the use of British bases in support of the American offensive operations against Iran reinforces the importance of the second key consideration – finding ways of aligning with Washington’s objectives that are politically palatable for 10 Downing Street. This is fundamentally about determining the art of the possible given competing priorities, while also reaffirming the UK’s credibility in Trump’s eyes (the only figure whose perspectives ultimately matter in the administration). Such credibility has suffered markedly owing to the dissonance at the start of Operation EPIC FURY.
Options for collaboration
Increased cooperation on some of the underlying challenges the Trump corollary seeks to correct would strengthen the bilateral relationship and benefit Britain. The diversification of critical mineral and rare earth element sources and the development of non-Chinese controlled supply chains through investment (both diplomatic and financial) in Latin and South America would address a key concern of the White House, while also providing economic benefits to the UK.
A practical effort from HM Government, and one that would be welcomed by Washington, would be the pursuit of defence and security in Britain’s own primary theatre of operations – the Euro-Atlantic, as identified in the Strategic Defence Review (SDR) – thereby enabling the US to pursue its own activities closer to home. This is effectively what the White House is pursuing: as the NDS notes, America is ‘sensibly and prudently pressing and enabling US allies and partners to take primary responsibility’.
Here, there is an area of overlap that will benefit both countries – Greenland and the North Atlantic. HM Government’s deployment of assets as part of ARCTIC SENTRY is a prudent move, illustrative of this concept in practice, and something already baked into the SDR. Additionally, this has the added benefit of addressing security in key strategic terrain also identified in the NDS.
While the US has prioritised the Western Hemisphere in its policy documents and through preliminary actions, it remains to be seen how much policy effort and energy Washington will dedicate to implementing the Trump corollary further.
There is also natural overlap on space-based cooperation between the two nations, as well as the Trump administration’s ambitions for ‘Golden Dome’: the continental missile defence system which the President seeks to field. The US$185 billion (£138.3 billion) programme will offer opportunities for UK-based defence companies, and bilateral cooperation could aid British national interest in enhancing its meagre Integrated Air and Missile Defence (IAMD) capabilities.
While the US has prioritised the Western Hemisphere in its policy documents and through preliminary actions, it remains to be seen how much policy effort and energy Washington will dedicate to implementing the Trump corollary further. Operation EPIC FURY and its regional expansion, to say nothing of other emergent geostrategic issues (precipitated by Trump or otherwise) could well consume greater American focus, making the corollary somewhat moot for the remainder of the President’s term in office.
Joshua C. Huminski is an International Fellow and the Council on Geostrategy, Senior Vice President for National Security and Intelligence Programmes, and Director of the Mike Rogers Centre for Intelligence and Global Affairs at the Centre for the Study of the Presidency and Congress.
This article is part of the Council on Geostrategy’s Strategic Defence Unit.
To stay up to date with Britain’s World, please subscribe or pledge your support!
What do you think about this Memorandum? Why not leave a comment below?
An interesting read. Where I diverge is that British agency and interests ought to be seen as more expansive than finding opportunities for alignment with Washington, especially when such alignment carries strategic risk. I agree completely, though, that the UK and Europe must carry more of the responsibility for security in the Euro-Atlantic. That said, greater strategic autonomy is the other side of that coin, which the US may not be fully prepared for.