Yu Koizumi (1982–) is a Japanese researcher specializing in military affairs and international security. After completing a master’s degree in political science at Waseda University, he worked at the Institute for Future Engineering, the Japanese Ministry of Foreign Affairs, the Russian Academy of Sciences’ Institute of World Economy and International Relations, and Japan’s National Institute for Defense Studies. He is currently an associate professor at the University of Tokyo’s Research Center for Advanced Science and Technology. His research examines Russian military and security policy, combining analysis of forces and weaponry with Russia’s concepts of sovereignty, regional order, and spheres of influence. His book “Ukuraina Senso” (“The War in Ukraine”), winner of the 2024 Shinsho Taisho, traces the political origins of Russia’s invasion, the capabilities and operations of both sides, and the changes that occurred on the battlefield.