Overview:
✓ Purpose: Designed to intercept and destroy airborne targets—such as aircraft, UAVs, cruise missiles, and ballistic missiles—at various ranges and altitudes.
✓ Developer: Almaz-Antey (Russia)
✓ Introduced: 2007 (first deployed by Russia)

Capabilities:
✓ Range: Up to 400 km (with the 40N6 missile)
✓ Target Altitude: From 100 feet to 30 km
✓ Detection Range: Up to 600 km
✓ Simultaneous Tracking: Can engage up to 36 targets simultaneously with 72 missiles

Global Use:
✓ India: Has signed a major deal with Russia (over $5 billion) for 5 S-400 system
✓ China and Turkey: Also operate S-400 units
✓ Controversies: U.S. has imposed or threatened sanctions (CAATSA) on countries purchasing S-400s