More than a year has passed since the outbreak of the Russia-Ukraine War. The assumption that Russia would easily beat Ukraine has turned out wrong. This is because of the uniqueness of war called “fog of war,” which means nobody can predict the future of warfare. The main reason for the protraction of the war can be ascribed to Russia’s failure to achieve air superiority. The “freedom of action” in warfare cannot be achieved without air superiority. Looking at the reasons why Russia has been unable to achieve air superiority, the answer can be found in four areas: command and control, doctrine and planning, education and training, and weapon system. We need to learn from the failure of the Russian Air Force and check and beef up our combat readiness posture in consideration of the changes in the strategic environment and of the new technological developments.