The US Navy’s Ship Self Defense System (SSDS) provides non-Aegis ships with an integrated self defense capability against anti-ship missiles and aircraft attack, originally optimized for close ranges and cluttered littoral environments where reaction times are extremely short. SSDS was mandated by Congress in 1991 following the attack on the USS Stark, building on the earlier Quick Reaction Combat Capability (QRCC) program. But by 2018, SSDS had evolved with improved blue-water and long-range shore-based anti-ship missiles, and now consolidates numerous efforts related to the integrated control of ship self defense (SSD) and multi-warfare combat direction for aircraft carriers and amphibious class ships. The Navy’s analysis and demonstration has established that surface SSD based on single-sensor detection point-to-point control architecture is inadequate against current and projected Anti-Ship Cruise Missile (ASCM) threats. The supersonic sea- skimming ASCM reduces the effective battle space to the horizon and the available reaction time-line to less than 30 seconds from first opportunity to detect until the ASCM impacts its target ship. Against such a threat, multi-sensor integration is required for effective detection, and parallel processing is essential to reduce reac- tion time to acceptable levels and to provide vital coordination/integration of hard-kill and soft-kill assets. Thus, though SSDS Mk 1 production is now complete and systems are in service aboard most planned ships, the SSDS Mk 2 continues as a major program aboard, in production, or planned for CVN-68/78, LHA-6, LHD-1, LPD-17, and LSD-41/49 surface ship classes. The Advanced Combat Direction System (ACDS) Block I is an earlier ship self-defense system, also developed by Naval and Maritime Systems (was Hughes, then Raytheon). ACDS had been in development since the mid-1980s, but was never fully developed and functional, and SSDS Mk 2 is replacing ACDS on the LHD-1 class.