From Strategy to Diplomacy: Colby’s Seoul Speech and the Operationalization of Flexible Realism

Under Secretary of War for Policy Elbridge Colby’s January 26 remarks at Seoul’s Sejong Institute represent the first significant diplomatic articulation of the operational logic underlying the 2026 National Defense Strategy.

Speaking in South Korea on his inaugural international trip, Colby translated the NDS’s sometimes abrasive rhetoric about burden-sharing into a coherent strategic framework centered on what the administration terms “flexible realism.”

The speech matters not for breaking new conceptual ground, the NDS established the policy foundations, but for demonstrating how these concepts function in actual alliance diplomacy with a model partner whose contributions to NATO defense have already demonstrated the power of the approach in practice.

The choice of Seoul as Colby’s first destination is itself strategically communicative, reflecting both the Indo-Pacific prioritization and recognition of South Korea’s proven contributions to global democratic defense.

South Korea represents what the administration considers the ideal alliance model: a partner with genuine military capacity, consistent defense investment above NATO averages, indigenous defense industrial capability, and clear-eyed recognition of threat proximity.

Critically, Seoul has already demonstrated its commitment to collective defense through substantial contributions to NATO’s defense industrial base and support for Ukraine, precisely the kind of global engagement that validates flexible realism’s core premise.

By opening with Seoul rather than traditional stops like Brussels or Tokyo, Colby signals that American prioritization will reward capability and commitment rather than diplomatic protocol or historical sentiment.

What makes this speech historically significant is how it crystallizes the transformation of the Ukraine war from a European regional conflict into a truly global contest that validates American strategic reorientation.

South Korea’s emergence as what General Pasquale Preziosa terms “a pivotal defense producer and standards partner” demonstrates that the two Koreas have, in different ways, exported their competition to Europe: Pyongyang through illicit ammunition supply and expeditionary force contributions to Russia, Seoul through legitimate industrial partnerships, technology transfer, and financial support to NATO allies and Ukraine.

This Indo-Pacific engagement in European defense provides the empirical foundation for the administration’s global burden-sharing framework.

Colby frames flexible realism as a correction to post-Cold War strategic drift: “For much of the post–Cold War period, American defense policy was shaped by abstractions, assumptions of permanent unipolarity, and ambitions that were untethered from geopolitical reality.” This critique echoes the NDS’s assessment that expeditionary operations eroded both homeland defense and the force structure necessary for peer competition.

The speech articulates flexible realism through four operational principles:

First, clarity about priorities, specifically identifying the Indo-Pacific as “the geopolitical hinge of the 21st-century” where “Americans’ long-term security, prosperity, and liberties will be decisively shaped.” This geographic prioritization aligns with the NDS’s resource allocation decisions, concentrating American military power where it’s genuinely irreplaceable.

Second, discipline about commitments. Colby’s repeated emphasis on “critical but limited support” translates the NDS’s burden-sharing framework into diplomatic language. The formulation acknowledges American contributions remain essential while establishing boundaries around what allies should reasonably expect.

Third, resolve about follow-through. The speech’s discussion of deterrence by denial along the first island chain demonstrates how strategic concepts translate into force posture. Colby emphasizes that deterrence succeeds “not when threats are loud but not backed up, but rather when outcomes are predictably favorable and credibly communicated.”

Fourth, seriousness about deterrence or the commitment to building “a military posture in the Western Pacific that ensures that aggression along the first island chain is infeasible, that escalation unattractive, and war is indeed irrational” reflects understanding that credible deterrence requires capability, not merely declarations.

This framework addresses what the NDS termed the “simultaneity problem” or the operational challenge of addressing multiple major threats concurrently with finite force structure. By prioritizing the Indo-Pacific while enabling allies to provide primary conventional defense in their regions, the strategy attempts to solve this mathematical problem through burden distribution rather than resource expansion alone.

The speech’s most diplomatically significant contribution may be its careful articulation of objectives toward China. Colby explicitly frames American goals: “We can and should strive for a stable, peaceful relationship with China that protects the interests of the United States and our allies. The United States under President Trump’s wise leadership does not seek to dominate China, nor do we seek to strangle or humiliate it.”

This formulation serves multiple audiences. For Beijing, it signals that American objectives are genuinely limited, preventing regional hegemony rather than regime change or economic strangulation. For allies, particularly those economically integrated with China, it offers reassurance that American strategy accommodates continued trade and engagement.

This is notable for a country such as Australia which clearly needs to sort out its economic engagement and dependence on China with its ability to defend itself against Chinese aggression, notably in the so-called “gray zone.” Australia is an information society and China directs threaten Australian systems through cyber intrusion among other things.

The emphasis on “a favorable balance of power in which no state can impose its hegemony” reflects classical balance-of-power logic rather than ideological competition. Colby acknowledges China’s “proud history” and frames competition as structural rather than civilizational. This approach contrasts with more ideological formulations that characterized previous administrations’ China strategies.

The operational manifestation, deterrence by denial along the first island chain, represents geographical and capability realism. Rather than attempting to dominate China’s littoral or contest every maritime feature, the strategy focuses on ensuring that decisive military action against allies along the island chain cannot succeed. This accepts Chinese military modernization as reality while ensuring it cannot translate into coercive leverage.

Colby’s emphasis on military diplomacy, noting that “the Secretary and I have already engaged with Chinese counterparts with respect and openness but also confident strength and clarity”, demonstrates integration of military power with diplomatic engagement. The NDS’s reference to “carrying the olive branch” finds practical expression in continued military-to-military communication focused on crisis management and risk reduction.

This approach differs fundamentally from containment. Cold War containment assumed Soviet objectives were fundamentally incompatible with Western interests, requiring comprehensive opposition. The current strategy instead assumes limited aims on both sides can coexist if backed by sufficient deterrent capability. Whether this assumption proves correct remains uncertain, but it at least offers a logical alternative to either permanent confrontation or accommodation.

Colby’s extended discussion of South Korea illustrates what the administration considers ideal alliance structure. He praises South Korea for understanding “geography, threat, and the centrality of concrete military power” and notes that President Lee’s decision to increase defense spending to 3.5% GDP “reflects a clear-eyed and sage understanding of how to address the security environment that we all face.”

This framing inverts traditional alliance rhetoric. Rather than American magnanimity protecting grateful allies, Colby argues South Korea’s increased investment primarily serves Korean interests: “It is in America’s interest to be sure, but even more, it is in South Korea’s interest.” This logic that capable allies enhance their own security more than they burden American resources represents core administration thinking.

The speech identifies specific Korean attributes that define model partnership: consistent defense investment above 2.5% GDP now increasing to 3.5%, indigenous defense industrial capacity producing globally competitive systems, mandatory conscription maintaining substantial mobilized force, geographic proximity to threat ensuring sustained commitment, and willingness to assume greater conventional defense responsibility.

These characteristics enable what Colby terms “proportionate contributions, and mutual benefit” as the foundation for sustainable alliance. South Korea can credibly provide primary conventional deterrence against North Korea, freeing American forces for broader Indo-Pacific missions while maintaining “critical but limited” American support for scenarios exceeding Korean capacity.

What Colby does not emphasize but what validates his model is South Korea’s already-demonstrated global contribution to democratic defense. As documented in my forthcoming book The Global War in Ukraine: 2021-2025, Seoul has emerged as a pivotal defense producer whose contribution to NATO’s defense industrial base demonstrates precisely the capability-based partnership Colby advocates. South Korea’s defense industry produces globally competitive systems, K9 howitzers serving multiple NATO armies, surface combatants built more efficiently than American yards can manage, advanced weapons systems that Polish army modernization relied upon for speed and cost-effectiveness over American alternatives.

Through legitimate industrial partnerships and technology transfer, South Korea has provided substantial material support to Ukraine and European allies, complementing financial aid flows to Kyiv. This represents the operationalization of burden-sharing years before Colby’s speech articulated the concept: a regional ally with indigenous capability extending its contribution to collective defense beyond its immediate theater, demonstrating that capable allies enhance rather than burden American security.

The strategic implication extends beyond Korea. If Seoul demonstrates that increased allied capability enhances rather than burdens American security, it validates the administration’s broader approach. European allies facing pressure to reach 3.5% can observe that South Korea’s investment translates into genuine capability and strategic autonomy rather than dependency and that this capability can be deployed globally to support collective democratic defense.

Moreover, South Korea’s contribution illustrates how the Ukraine war has become the crucible through which the future global order is being forged. The integration of Japanese space assets, South Korean production capacity, and European industrial bases into a single war-support ecosystem previews how the next generation of deterrence will be organized. This is the empirical validation of flexible realism: allies with genuine capability can contribute across theaters, creating burden-sharing that makes American global commitments more sustainable.

Colby’s discussion of South Korea assuming “greater responsibility for South Korea’s conventional defense” against North Korea reflects the NDS’s theater-specific burden allocation. Given South Korea’s economic and military advantages over Pyongyang, Korean forces should credibly deter conventional attack. American contributions—nuclear deterrence guarantees, strategic ISR, specialized capabilities—provide what Korea cannot replicate while avoiding permanent large-scale ground force presence.

This model, if replicated, would allow American force redistribution across the Indo-Pacific to address China challenges while maintaining alliance commitments. The speech suggests this is precisely the intent: American forces currently concentrated on the Korean Peninsula might better serve broader regional deterrence while Korea fields sufficient conventional capability independently.

The Ukraine war has revealed a stark contrast in how the two Koreas engage with European security, illuminating both the promise and peril of Indo-Pacific involvement in what was initially framed as a regional conflict. This contrast validates Colby’s emphasis on capability-based partnerships while demonstrating the global nature of contemporary strategic competition.

North Korea has transformed from ammunition supplier to expeditionary force participant, deploying combat troops to fight alongside Russian forces on European soil for the first time since the Korean War. Pyongyang supplies massive quantities of artillery shells and ballistic missiles to Moscow, while acquiring unwelcome expertise in electronic warfare and counter-UAS operations that will echo on the Korean Peninsula. This represents the authoritarian axis in practice: transactional burden-sharing where Pyongyang trades ammunition and manpower for Russian energy, hard currency, and military technology.

The presence of North Korean forces in Europe fighting against a democratic state supported by NATO illustrates how thoroughly the Ukraine war has become a system-defining global contest. What began as Russia’s attempt to revise European borders has evolved into a conflict where Asian authoritarian powers provide decisive military support, effectively treating European security as inseparable from their own strategic competition with the United States.

Seoul’s response validates the administration’s model of capable allies contributing globally to collective defense. Through legitimate industrial partnerships, South Korea has provided substantial support to Ukraine and NATO allies without deploying forces or violating its own arms export policies. Korean defense systems now serve on NATO’s eastern flank: K9 howitzers provide artillery capability to Poland and other frontline states, Korean air defense systems supplement European capabilities, and Korean shipbuilding expertise contributes to allied naval modernization.

This contribution demonstrates several strategic realities. First, that indigenous defense industrial capability enables global burden-sharing: South Korea can support European allies because its own defense industry produces systems competitive with or superior to American alternatives. Second, that capable allies can extend their contribution beyond their immediate theater when collective security is at stake: Seoul’s support for NATO defense strengthens deterrence against the authoritarian axis globally, including in the Indo-Pacific. Third, that such contributions enhance rather than burden American security: Korean systems filling gaps in European defense free American resources for Indo-Pacific priorities.

As General Preziosa observes in his foreword to The Global War in Ukraine: 2021-2025, the war in Europe has reformatted Asian security by exporting the Korean competition to a new theater. The two Koreas now confront each other not only across the DMZ but also through their support for opposing coalitions in Ukraine. Pyongyang backs Moscow with illicit ammunition and expeditionary forces; Seoul supports NATO and Ukraine through legitimate industrial partnerships and technology transfer.

This exported competition validates several of Colby’s key arguments. It demonstrates that Indo-Pacific security and European security are no longer separable: the same authoritarian axis threatening Taiwan supports Russia’s war in Ukraine, while the same democratic partners defending European order recognize their stake in Indo-Pacific stability. It shows that alliance value depends on capability rather than geography: South Korea’s contribution to NATO defense matters more than many formal NATO members’ contributions. And it illustrates that burden-sharing works when allies have genuine capacity: Korea can support collective defense globally because its decades of investment in indigenous capability created exportable systems and industrial depth.

The contrast also illuminates the character of authoritarian versus democratic coalitions. North Korea’s contribution is purely transactional, ammunition and troops for energy and technology, with no broader alignment of interests or values. South Korea’s contribution reflects shared commitment to sovereignty, territorial integrity, and collective defense, extended globally because Seoul recognizes that democratic order is indivisible. The authoritarian axis operates as a marketplace; the democratic coalition, despite all its coordination challenges, operates on principle backed by capability.

The Korean involvement in Ukraine carries direct implications for Indo-Pacific security. North Korean forces gain combat experience and tactical lessons that will inform their approach to any future Korean Peninsula conflict. Russian technology transfer to Pyongyang, potentially including advanced missile, submarine, or space systems, could materially strengthen North Korea’s threat to South Korea, Japan, and American forces. The authoritarian axis coordination demonstrated in Ukraine establishes patterns that could be replicated in a Taiwan scenario: China providing industrial and financial lifelines, North Korea contributing munitions and potentially forces, Russia offering diplomatic cover and specialized capabilities.

Conversely, South Korea’s contribution establishes precedents for democratic coalition coordination across theaters. If Seoul can support European allies effectively, the model extends to other scenarios: European states supporting Indo-Pacific partners, Middle Eastern democracies contributing to collective defense, a genuinely global network of capable democracies providing mutual support. This is the operationalization of flexible realism on a global scale: American power concentrated where irreplaceable, allied capability distributed where effective, coordination across all theaters to address a transnational authoritarian challenge.

The Ukraine war has thus become the testing ground for the strategic concepts Colby articulates. South Korea demonstrates that capable allies with indigenous defense industrial capacity can contribute globally to collective defense. North Korea demonstrates that authoritarian powers will support revisionist aggression transnationally when it serves their interests. The outcome in Ukraine will therefore shape not only European security but also the credibility of deterrence in the Indo-Pacific: if the authoritarian axis succeeds in Europe despite democratic opposition, Beijing will draw conclusions about Taiwan; if the democratic coalition prevails, the lesson will be that capable allies coordinating across theaters can contain revisionist powers.

Colby’s speech operationalizes the NDS’s incentive-based alliance approach through diplomatic recognition. By making Seoul his first international destination and explicitly praising South Korea as “a model ally,” he demonstrates the rewards for meeting American expectations. This creates observable incentive structures for other allies: those matching Korean commitment levels receive enhanced cooperation and prioritization.

The speech’s discussion of NATO burden-sharing provides context: “For a generation, polite American pleas to Europeans to spend more on defense fell on deaf ears. Rather, Europeans effectively calculated that they could continue to underspend and America would, motivated by gauzy abstractions like the ‘rules-based international order,’ still hold the bag.” Colby credits Trump’s confrontational approach with achieving what diplomatic entreaties could not: “our NATO allies — after decades of underinvestment — have pledged to meet what the National Security Strategy and National Defense Strategy declare as a new global standard of allied defense spending: 3.5% of GDP.”

This narrative suggests that previous alliance management, prioritizing diplomatic comity over operational outcomes, failed to generate necessary capabilities. The current approach instead applies market logic: alliances are strongest when partners share risks proportionally, and American engagement should reward contribution rather than simply respond to need.

The extension to Asia proves strategically significant. Colby states explicitly: “these principles apply as much in Asia as they do in Europe.” This universalization of burden-sharing standards prevents allies from claiming exemptions based on regional circumstances or historical relationships.

The practical implications extend beyond spending levels to operational collaboration. The NDS called for reducing “defense trade barriers in order to maximize our collective ability to produce forces required to achieve U.S. and allied defense objectives.” Colby’s praise of South Korean defense industry, implicitly acknowledging Korean systems’ global competitiveness, suggests genuine willingness to integrate allied production into American acquisition.

South Korea’s defense industrial success demonstrates what the NDS’s industrial integration vision could achieve. Korean shipyards build surface combatants more efficiently than American yards. Korean K9 howitzers serve multiple NATO armies. Polish army modernization relied primarily on Korean rather than American systems for speed and cost-effectiveness. If the United States embraces rather than resists this reality, allied defense industries become force multipliers rather than competitors.

Colby’s articulation of deterrence by denial along the first island chain provides operational specificity to the NDS’s Indo-Pacific strategy. He describes “a resilient, distributed, and modernized force posture across Japan, the Philippines, the Korean Peninsula, and elsewhere in the region, a posture optimized for a denial of quick or decisive gains through military force.”

This formulation reflects understanding that peer conflict differs fundamentally from expeditionary operations. Against China, American forces cannot assume air superiority, sanctuary bases, or logistics dominance. Deterrence therefore requires denying Chinese ability to achieve fait accompli, rapid seizure of Taiwan or other territory before American reinforcement.

The emphasis on resilience and distribution addresses Chinese strike capabilities. Concentrated American bases in Japan and Korea present lucrative targets for Chinese missiles. Distributed posture across multiple locations, with forces capable of continuing operations after initial strikes, complicates Chinese targeting and raises operational costs.

Colby’s description that such posture “binds us together in our shared pursuit of peace and stability” suggests alliance integration is operational necessity, not diplomatic preference. Distributed operations across allied territory require host nation support, access, and cooperation. This creates mutual dependencies, American capability depends on allied hosting, while allied security depends on American power projection.

The speech’s discussion of military-to-military communication with China situates deterrence within risk management frameworks. Colby notes continued engagement “focused on strategic stability, crisis management, and reducing the risk of miscalculation and miscommunication.” This acknowledges that even with robust deterrent posture, incidents, accidents, and crises will occur. Communication channels reduce escalation risks without softening deterrent commitments.

Colby’s repeated invocation of “decent peace” as the strategic objective merits examination. He defines this as “a reasonable equilibrium that works for Americans, for our allies, and indeed for the whole region.” This formulation accepts that peace requires accommodation of legitimate interests, including China’s.

The emphasis on equilibrium rather than dominance reflects recognition of constraints. The United States cannot militarily dominate China’s littoral in the way it dominated Iraq’s airspace. China’s geographic proximity, industrial capacity, and growing military sophistication ensure it will maintain substantial regional influence. The question is whether that influence translates into hegemony or coexists with allied autonomy.

Colby’s statement that “sovereignty is respected” and the order should be “adaptive and emergent, not formalistic, hidebound” suggests acceptance of Chinese participation in regional governance, provided it doesn’t extend to veto power over allied decisions. This contrasts with more rigid formulations that treated any Chinese influence as inherently threatening.

Whether Beijing accepts this framework remains uncertain. Chinese strategic commentary often questions whether American presence along the first island chain can coexist with Chinese security. If Chinese strategists view American forces in Japan, Korea, and Philippines as inherently threatening, deterrence by denial may be seen as containment regardless of American intentions.

Colby’s framework at least offers logical coherence: the United States prevents Chinese hegemony while accepting Chinese power, China accepts American presence while building capability to deny American dominance. Whether such mutual deterrence stabilizes or drives arms racing depends on implementation and Chinese strategic choices.

Colby’s Seoul speech demonstrates how the 2026 NDS’s strategic concepts translate into alliance diplomacy. The emphasis on South Korea as model partner operationalizes incentive structures rewarding allied capability. The articulation of limited aims toward China provides diplomatic framework for military strategy. The discussion of deterrence by denial offers operational specificity to abstract commitments.

What strengthens these concepts beyond rhetoric is South Korea’s already-demonstrated contribution to global democratic defense. Seoul’s support for NATO’s defense industrial base and Ukraine validates the core premise of flexible realism: that capable allies with indigenous defense capacity can contribute across theaters, enhancing rather than burdening American security. The contrast with North Korea’s support for Russia illustrates how the same geographic theater generates opposing contributions, authoritarian burden-sharing through illicit ammunition and expeditionary forces versus democratic burden-sharing through legitimate industrial partnerships and technology transfer.

The global war in Ukraine thus serves as both validation and test of the administration’s strategic framework. It demonstrates that contemporary security challenges are transnational: Asian powers shape European outcomes, European industrial capacity supports Indo-Pacific security, and the authoritarian axis coordinates across all theaters. It proves that capable allies matter more than treaty formalities: South Korea’s contribution to NATO defense exceeds many formal members’ contributions. And it shows that burden-sharing requires genuine capability: Seoul can support collective defense globally because decades of investment created exportable systems and industrial depth.

Several tensions remain unresolved. Whether allies beyond South Korea will achieve the capabilities necessary for the “critical but limited support” model remains uncertain. Whether China interprets American first island chain posture as legitimate deterrence or unacceptable encirclement will shape stability prospects. Whether American domestic politics sustain costly alliance commitments absent European ground force deployments or visible allied dependency is unknown.

But the speech at least demonstrates strategic coherence, matching diplomatic articulation with operational concepts and alliance management with force posture requirements. As argued in examining the NDS, the strategy attempts to align commitments with capabilities through prioritization, allied empowerment, and industrial integration. Colby’s remarks show how this alignment functions in diplomatic practice, using South Korea to exemplify what sustainable collective defense might resemble.

The fundamental test remains implementation. Strategic documents and diplomatic speeches establish frameworks; operational reality determines whether those frameworks prove sustainable. Whether flexible realism generates the allied capabilities, industrial capacity, and deterrent credibility it assumes will determine whether this represents genuine strategic coherence or optimistic projection.

Yet Colby’s Seoul speech, viewed against the backdrop of South Korea’s already-demonstrated contribution to the global war in Ukraine, suggests this is more than aspirational thinking.

Seoul has operationalized burden-sharing years before the NDS articulated the concept. Korean defense systems now serve NATO allies on the eastern flank. Korean industrial capacity contributes to Ukrainian defense. Korean investment in indigenous capability enables global contribution to collective defense.

This is flexible realism in practice, demonstrating the administration’s ability to translate strategic concepts into diplomatic practice and operational reality with at least one key partner, suggesting the potential for broader application if other allies prove willing to follow South Korea’s model.

Note: My book The Global War in Ukraine: 2021-25 along with the published essay about the war based on that book will be published on February 15, 2026 and available on Amazon in e-book and paperback form.