For the first time, two nuclear-armed adversaries of the United States have joined forces on the battlefield. As of March 2025, North Korea has deployed an estimated 11,000 troops to roll back Ukraine’s gains in western Russia. This assistance, which has bolstered Russia’s battlefield position, marked growing cooperation between the two regimes. The deployment also raised the question: what’s in it for Pyongyang?
In addition to fuel, conventional weapons, and money, one component of this cooperation may be technological assistance for North Korea’s nuclear missile programs. Russia’s reported support for the North’s space program may benefit Pyongyang’s intercontinental ballistic missile (ICBM) program. And U.S. officials expect that Russian assistance will expand to include direct support for North Korea’s missile and submarine programs.
Given Russia’s technological support, North Korea will likely continue to expand and improve its nuclear forces. The United States should prepare for the assurance challenges posed by a larger and more survivable North Korean nuclear force by enhancing U.S. allies’ intelligence-surveillance, and reconnaissance (ISR) capabilities, establishing a trilateral intelligence sharing arrangement with Japan and South Korea, and fast-tracking the development of a nuclear-armed sea-launched cruise missile (SLCM-N).
Russia’s Shifting Position
Historically, Russia has taken an active role in international counterproliferation efforts against North Korea’s nuclear program. The Soviet Union was the central voice in urging North Korea to join the Nuclear Nonproliferation Treaty, and, following the 1994 nuclear crisis, Russia proposed a six-party diplomatic conference to reach a resolution. North Korean officials credited Russia’s peaceful approach during the Six Party Talks as critical to the outcome of the 2005 round of talks, which nearly resulted in Pyongyang abandoning its nuclear weapons program
Even following the failure of the Six Party Talks, Moscow continued to push for denuclearization: the Kremlin condemned North Korea’s nuclear test on October 6, 2006, and supported the imposition – and subsequent strengthening – of U.N. sanctions. Russia cemented its desire for denuclearization in its 2016 Foreign Policy Concept document, which stated that “Russia has always championed a non-nuclear status for the Korean Peninsula and will support its denuclearization.”
The strain of the war in Ukraine, however, has prompted the Kremlin to trade nuclear-related technologies for ammunition and battlefield aid. As of April 2025, Russia is sharing technologies related to submarines, stealth aircraft, and missile design with China and unspecified nuclear and space technologies with Iran in return for weapons, ammunition, and support for Russia’s defense industry. Russian assistance to North Korea, while limited, may benefit North Korea’s ICBM program, and has the potential to expand given Pyongyang’s support for the Kremlin’s war effort and the deepening ties between the two states.
Implications for U.S. and Allied Security
Russia’s growing technological assistance has the potential to bolster North Korea’s development of critical technologies: ICBMs and submarine-launched ballistic missiles (SLBMs), nuclear-powered submarines, and low yield nuclear weapons. Pyongyang has yet to master key technologies related to reentry vehicle reliability, accuracy, and warhead miniaturization. Russian technological assistance could help the North overcome these obstacles and speed its efforts to develop miniaturized, low-yield nuclear warheads and nuclear-powered submarines.
Russian assistance with North Korea’s space program could benefit the North’s ICBM program. Russian President Vladimir Putin first offered to provide technological assistance for North Korea’s space program in September 2023, when he met with Kim Jong Un to discuss opportunities for deeper cooperation. Two months later, South Korean officials announced that, thanks to Russian assistance, North Korea had successfully launched its first spy satellite. The precise nature of Russia’s support for North Korea’s satellite launch program is unclear, but there is significant overlap in the technologies used in space launch vehicles and ICBMs, as illustrated by the fact that the rockets North Korea used in two of its satellite launches used ICBM technology.
There is also a growing risk that Moscow’s support for North Korea will expand to include direct assistance with sensitive technologies related to nuclear weapons, long-range missiles, or submarines. U.S. Indo-Pacific Command (INDOPACOM) Commander Samuel Paparo said in April 2025 that North Korea is attempting to gain assistance in missile and submarine technology from Russia in exchange for support in Ukraine.
An improved North Korean nuclear force will pose a credibility challenge for the United States. If Russian assistance allows North Korea to enhance the reliability of its ICBMs or develop SLBMs that can reliably target the U.S. homeland, the North may be emboldened in pursuing regional aggression under the belief that the United States will be more reluctant to respond. Further, if North Korea develops a credible second-strike capability and an ability to strike the U.S. homeland, existing concerns in South Korea about U.S. extended deterrence commitments would likely intensify.
The Way Ahead
Given the substantial strategic challenges that a more capable North Korean nuclear force will pose to the United States and its allies, the Trump administration should prepare for those challenges now, rather than waiting until they become apparent.
First, the Trump administration should enhance regional deterrence by bolstering Japanese and South Korean ISR capabilities. The creation of multiple centers of decision will complicate Kim Jong Un’s calculus when contemplating aggression against U.S. allies. Japan and South Korea, however, lack the indigenous ISR capabilities necessary to support a fully independent long-range strike capability. To accelerate these efforts, the Trump administration should promote greater collaboration between U.S., Japanese, and South Korean industry.
Second, the United States should establish a formalized, trilateral information and intelligence sharing arrangement with Japan and South Korea to track developments in North Korea’s nuclear and missile programs. Intelligence sharing would further enhance the allies’ cooperation by ensuring that they have access to the same set of information about North Korean forces and may bolster confidence in U.S. security assurances.
Third, the new administration should fill a deterrence gap in the Indo-Pacific by fast-tracking the development of the SLCM-N. Current U.S. strategic forces are ill-suited to respond to a low yield nuclear attack – a growing threat for U.S. allies in the region. SLCM-N will address that gap by providing the president with a flexible, low yield response option.
There is likely little that the United States can do to prevent North Korea from continuing to expand and improve its nuclear forces. It remains uncertain whether the Kremlin has any interest in returning to its prior nonproliferation commitments. Until Russia does so, the United States may need to accept North Korea’s nuclear modernization as an unfortunate reality. The Trump administration should prepare accordingly to deter aggression and assure U.S. allies.