September 19, 2025
Jim Lamson and Hanna Notte
Executive Summary
Key takeaways
(1) Cooperation continues. Over the course of 2024 and spring 2025, defense cooperation between Iran and Russia continued. The countries’ adoption of the Treaty on Comprehensive Strategic Partnership capped a string of other activities, including numerous high-level political-military meetings and transfers of select defense technologies. Iran delivered Fath-360 ballistic missiles to Russia and continued to assist Russia’s UAV production. Most assistance, however, flowed from Russia to Iran, especially in the aerospace, ground, and space domains.
(2) A year of upheaval. Silhouetted behind these general trends, a confluence of geopolitical, regional, and battlefield developments fueled a growing asymmetry in the defense relationship. The DPRK emerged as an increasingly important supporter of Russia’s war against Ukraine; Israel’s campaign against the “axis of resistance” and Iran itself ushered in a new era of strategic vulnerability for Iran; in spring 2025, the U.S. administration began to engage Moscow diplomatically, potentially affecting Russia’s calculus regarding cooperation with Iran, at least in the most sensitive areas; and finally, in mid-June, Israel (eventually joined by the United States) engaged in a short aerospace conflict with Iran.
(3) A growing asymmetry in needs. Israel’s campaign against Iran and the “axis of resistance” damaged the country’s military-defense assets and exposed key shortcomings, forcing Iranian strategic planners back to the drawing board. Strategically more vulnerable, Iran’s preexisting appetite for Russian assistance in areas such as long-range strike, air and missile defenses, and naval denial has only grown further. For Russia, which expanded the local production of Shahed drones, diversified its sourcing of UAV components, and shifted to focus on other UAV designs, reliance on Iran has passed its peak. Though Russia may well remain interested in production technology for the Shahed-238 drone and its variants as well as Iran’s transfer of other drones and even missiles to enable more diverse strike packages, its dependence on Iran to meet battlefield needs in Ukraine is presently trending downward.
(4) The pendulum swings back. While both partners likely retain an interest in sharing lessons from their respective military campaigns, and while a degree of institutional inertia may propel defense cooperation, we observe a shift toward an increasingly asymmetric partnership, with Iran far more dependent on Russia than vice versa. Full battle damage assessments from the Israel-Iran aerospace conflict, the trajectory of battlefield conditions in Ukraine, and the extent of Chinese assistance to both Russia and Iran, are among the factors that will determine how far the pendulum will swing back toward a more asymmetric Iran-Russia defense partnership.
(5) Imagining different futures. Based on developments since 2024 that have affected Iran’s and Russia’s defense needs from each other, as well as the drivers and constraints shaping the defense relationship, we consider a continued strategic partnership to be the most likely future. Other futures—a limited military alliance, a full military alliance, or a breakup—are less likely, though not altogether inconceivable, assuming certain contingencies.
