Long-range strikes by the Alpha Special Operations Center of the Security Service of Ukraine ( SBU ) unit have severely damaged key elements of Russia ’s layered air defense system, with losses estimated at about $4 billion. According to an SBU statement published on Telegram , Ukrainian forces have destroyed or disabled multiple Russian air defense systems over the past year, including S-300, S-350 and S-400 systems, Buk-M1 and Buk-M2 surface-to-air missile systems, Pantsir-S1 and Pantsir-S2