During the Cold War, the Soviet Union knew its numerous air forces were no match for the combined Western power. This imbalance partly drove it to invest heavily in air defense. It pioneered air defense systems, rendering the XB-70 Valkyrie obsolete before it could enter service and downing the high-flying U-2 spy plane during the Cuban Missile Crisis. Today, Russia possesses impressive layered air defense systems made up of the long-ranged S-500, S-400 (an upgraded S-300), S-300, and S-200 and the medium-ranged Panstir and Buk air defense systems. This article will focus on the S-400 and S-300 air defense systems.