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Surface-to-air (SAM) systems are military defense platforms designed to detect, track, and intercept aerial threats from ground or sea. They typically include radar and sensor networks, fire-control and command-and-control units, and missiles launched from fixed or mobile launchers. Modern SAMs operate as part of an integrated air defense system (IADS) that links multiple sensors, interceptors, and command posts to increase detection range, tracking accuracy, and response speed.

Development of SAM technologies accelerated during the Cold War, yielding increasingly capable short-, medium-, and long-range systems. Notable examples include early Western and Soviet designs such as the Nike Hercules and S-75 Dvina (SA-2 Guideline), as well as later families like the S-300/400 and THAAD. Naval variants exist as well, and many modern systems are networked to share sensor data and coordinate engagements across a battlefield or theater.

Guidance methods vary among SAMs. Some missiles are cue-guided by ground-based radars (command guidance or semi-active radar homing), while others carry their own seekers for terminal guidance (active radar or infrared). Launch platforms range from fixed batteries to mobile launchers and ships. Systems are typically categorized by range and altitude performance into short-range, medium-range, and long-range classes, each suited to different roles such as point defense or area high-altitude interception.

Modern SAM networks protect critical infrastructure, military bases, cities, and other high-value assets, and are deployed by many nations in both defensive and expeditionary operations. Effectiveness depends on sensor coverage, countermeasures, interoperability with other air-defense assets, and the speed and maneuverability of interceptors. See also air defense and ballistic missile defense.