‘Trump Doctrine’ A Fundamental Challenge to Allied Unity

The Diplomacy, Information, Military, and Economics (DIME) of the Trump Doctrine

In diplomacy, the Trump administration maintains the view that regional conflicts should primarily be addressed by local actors. This may appear isolationist, but the concept is not new. During the Obama administration, the U.S. adopted a “lead from behind” posture in Libya, expecting the U.K. and France to lead military operations. And when strategic interests are minimal, Washington has shown a readiness to reconsider its involvement. In his first term, Trump quietly negotiated with the Taliban to reassess U.S. efforts in Afghanistan—moves that laid the groundwork for the full withdrawal of U.S. troops in 2021.

In his second term, Trump and his foreign-policy team have invested a great deal of political and diplomatic capital into a peace deal with Russia, often giving the impression that Ukraine’s demands are secondary. Compared to NATO’s traditional approach, Trump’s vision downplays longstanding alliances and revisits historical commitments in the context of the current strategic environment.

In information, strategic communications plays a central role. For instance, the Trump administration emphasizes ideological rivalry by repeatedly using the term “Chinese Communist Party,” framing China as a systemic threat. The “fall” of Afghanistan and the failure of deterrence in Ukraine are cast as previous policy failures, reinforcing Trump’s message that peace must be maintained through strength.

In military affairs, restoring deterrence — shaken by the Russian invasion of Ukraine and Chinese threats against Taiwan — is vital. Yet this does not necessarily mean a return to major unilateral U.S. deployments. Since the Cold War, U.S. troop levels in Europe have declined. In the 1950s, some 450,000 troops were stationed there; by the late 1980s, that number was around 300,000.

After the Soviet collapse and the 2003 Iraq War, U.S. forces were cut to roughly 60,000, with missions shifting toward supporting operations in the Middle East and Africa. Russia’s 2022 invasion of Ukraine reversed this trend, underscoring the need for visible U.S. military presence. Since then, 22,000 additional troops have been deployed, raising total U.S. forces in Europe to about 100,000.

One key development is the repositioning of U.S. Army forces in Europe. The establishment of the V Corps headquarters in Poland marked the first forward-based command in Europe since the Cold War. While deployments remain rotational in line with previous agreements, the V Corps now acts as a key anchor for NATO’s eastern defenses.

In economics, the Trump administration aims to be a game-changer by setting numerical targets. U.S. Secretary of Defense Pete Hegseth declared that revitalizing NATO begins with increased spending. In February, just weeks after Trump took office, his administration outlined its defense priorities: restoring the transatlantic defense industrial base, accelerating the adoption of new technologies, improving readiness and lethality, and building credible deterrence.

And, clearly, as we’ve seen in Europe and in the Indo-Pacific, U.S. allies are expected to commit to more defense spending. At the NATO summit in June, member states agreed in principle to spend 5% of GDP on defense, although only 3.5% is dedicated to direct military outlays and the remaining 1.5% includes cybersecurity and infrastructure, allowing national discretion.

Also in the economic realm, the European Union’s moves warrant attention. In March, the EU published its first “White Paper for European Defence,” emphasizing the need to close capability gaps in missile defense, drones and cyber warfare. It also announced a €15 billion defense financing initiative. In addition, the EU has moved closer to NATO’s position, prioritizing secure and timely arms delivery to Ukraine.

What Are the Implications of Trump’s NATO Strategy for Alliances in the Indo-Pacific?

Once again, applying the DIME lens offers insight into potential shifts. In diplomacy and information, Trump is likely to prioritize competition among great powers, focusing especially on China, which he labels a systemic threat. This will likely increase U.S. engagement on peace and stability in the Taiwan Strait. In this environment, direct cooperation with regional allies will gain prominence, while global coalition-building may take a backseat—a departure from the multilateralism of former U.S. President Joe Biden.

At the 2024 NATO summit in Washington, Biden invited the IP4 countries— Japan, South Korea, Australia, and New Zealand—alongside Ukraine and the EU, highlighting global outreach. Such moves may be scaled back under Trump. Meanwhile, increased unilateral pressure on allies — as we’ve witnessed lately with India — has the potential to backfire, pushing longstanding allies away from the U.S.

In the military domain, Trump’s transactional approach could challenge alliance cohesion. In his first term, Trump declared that “all options are on the table” regarding North Korea, signaling potential escalation up to nuclear conflict. This created strategic ambiguity designed to deter adversaries.

While pursuing a possible deal with Russia, Trump is also expected to retain the option of escalation, yet this stance risks unsettling allies who seek predictability and assurance. Since 2022, Russia’s frequent references to tactical nuclear weapons have reinforced the urgency of nuclear deterrence. Strengthening extended deterrence in Europe and the Indo-Pacific will be a major challenge throughout Trump’s second term. Economically, Trump’s success in pushing NATO toward the 5% GDP defense target will ripple into the Indo-Pacific. At the 2024 summit, the IP4 countries (Australia, Japan, South Korea and New Zealand) endorsed a 2% target. Under Trump, however, that number is considered too low, and the U.S. will almost certainly demand it be raised nearer NATO levels.

Ultimately, the “Trump Doctrine” poses a fundamental challenge to allied unity and the future of collective defense. How global alliances manage the risks and costs of escalation therefore remains a crucial test.

（Photo Credit: NurPhoto / Getty Images)

Tomonori Yoshizaki

Visiting Professor, Institute of Japan Studies, Tokyo University of Foreign Studies

Tomonori Yoshizaki is Project Professor at the Institute of Global Studies, Tokyo University of Foreign Studies, and Visiting Professor of International Security Studies at the National Graduate Institute for Policy Studies (GRIPS). His expertise lies in alliance relations, including NATO, and European international politics. After completing his undergraduate and master’s studies in political science at Keio University, he joined the National Institute for Defense Studies (NIDS), the research arm of Japan’s Ministry of Defense. He went on to serve as Director of Theoretical Studies, Special Research Fellow for Policy Simulation, and Secretary of Research, before assuming his current position at Tokyo University of Foreign Studies in April 2023.

As part of the university’s new JV-Campus initiative, he delivers online lectures on Peace and Conflict in the Indo-Pacific and Re-designing Japan’s Future Vision. He has also been a visiting fellow at King’s College London and at the Hudson Institute in Washington, D.C. His recent publications include The Impacts of the Russo-Ukrainian War (co-authored, Springer, 2025) and The Geopolitics of National Defense as Revealed by Japan’s Top Self-Defense Force Leaders (co-authored, PHP Institute, 2025).

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Disclaimer: The views expressed in this Geoeconomic Briefing do not necessarily reflect those of the API, the Institute of Geoeconomics (IOG), or any other organizations to which the author belongs.

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