<p>How have the two Koreas reacted to the Ukraine war? How has the war changed the security dynamics in Northeast Asia? Of all the security maneuvers undertaken by various states, North Korea’s dispatch of tens of thousands of soldiers to fight for Russia stands out as one of the most audacious. Meanwhile, the significance of South Korea—a vital supplier of weaponry to Ukraine’s neighbors unsettled by the war—should not be underestimated. To understand the strategic calculations shaping the behavior of the Koreas, we adopt a holistic approach that considers both their associations with great powers and the regional dynamics. North Korea’s military intervention was motivated by a desire to establish superiority over the South and to reduce its dependence on China—an opportunity that Moscow seized during its time of need for external support. South Korea, on the other hand, has had to balance the strategic imperative of not antagonizing Russia with mounting Western pressure. The two Koreas’ disparate entanglements amply attest to the growing security interconnection between East Asia and Europe—two geostrategic theaters hitherto conventionally considered separate. With Donald Trump’s erratic trade and foreign policies, further integration into a Eurasian security complex may be spurred by unpredictable interactions among the major actors concerning the Ukraine war, Korean affairs, and Taiwan.</p>