The Phalanx CIWS is a U.S. Navy radar-guided 20mm Gatling gun system designed as a ship's last line of defense against incoming missiles, aircraft, drones, and small boats. Development began in the 1970s by General Dynamics (later Raytheon) to counter sea-skimming anti-ship missiles; the Block 0 entered service in 1980 on USS Coral Sea, firing 3,000-4,500 rounds per minute with full radar search, track, and auto-engage capability. Upgraded versions like Block 1B added FLIR sensors for surface th