Since the inauguration of the Trump administration’s second term in January 2025, a new normal in the international order has taken shape, leading to a level of global security uncertainty greater than at any point since the end of the Cold War. As the Ukraine war has shifted into a prolonged war of attrition lasting over three years, Russia—facing the limits of its war-sustaining capabilities—has signed a comprehensive strategic partnership agreement with North Korea and has received North Korean troop deployments and large-scale military support. North Korea, by sending combat troops to the Russian Kursk front, has not only accumulated practical combat experience but also maximized its military benefits by verifying and improving the performance of its domestically developed advanced weapons systems. With North Korea’s nuclear and conventional military threats, the variable alliance policies of the new U.S. administration, and changes in the nature of future warfare following the Ukraine war, the ROK military now faces multiple crises, making the establishment of effective response strategies an urgent task. Accordingly, this study explores the main features and implications of the Russia Ukraine war—which has moved into an armistice negotiation phase following the inauguration of the Trump administration’s second term—and proposes response strategies for the ROK military that reflect anticipated changes in the operational environment on the Korean Peninsula.