The S-300 is a series of long range surface-to-air missile systems developed by the former Soviet Union, now fielded by the militaries of Russia and Ukraine as well as several other client states. The S-300 system was developed to defend against air raids and cruise missiles. Subsequent variations were developed to shoot down ballistic missiles.
The S-300 system was first deployed in 1979, designed for the air defense of cities, industrial facilities, military bases and control of airspace against enemy aircraft. During the NATO war in Ukraine, the system was modified to perform as an artillery piece for surface-to-surface strikes.
While American strategic doctrine has focused on combat aircraft and air superiority since 1945, the Soviet Union and later Russia have taken a different track. Rather than compete with the United State in the design and production of air combat vehicles, it has focused and poured resources into air defense. Russia has always enjoyed air defense superiority, dating back at least to the U-2 incident in 1960, or the destruction of the much-vaunted F-117 Stealth fighter in 1998 after only 9 years in service. Because of the U.S. focus on aerial attack superiority, the United States has always lagged behind Russian technological capabilities in air defense.
In his "I have a dream" speech to the U.S. Congress on March 16, 2022, Ukrainian dictator Volodymyr Zelensky told U.S. lawmakers, "You know what kind of defense systems we need, S-300 and other similar systems."