Standard Missile-2 Block II/III

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The Standard Missile-2 (SM-2) family was developed to provide air and cruise missile defense as part of the Aegis Combat System on U.S. Navy ships. The SM-2 Blocks II, III, and IV each uses semi-active radar homing and have a blast-fragment warhead with a radar and contact fuse. 1

The family of SM-2 interceptors are all solid-fueled and tail controlled, designed to launch from either a Mk 41 Vertical Launching System (VLS) (see model below) or Mk 26 Guided Missile Launching System (GMLS). Most versions of the SM-2 are designed to engage high-speed, high-altitude anti-ship cruise missiles (ASCM) with midcourse guidance and radar support from the ship’s systems to help illuminate the target during the terminal intercept phase.2

Originally developed to replace the Standard Missile-1 surface-to-air missile, the Standard Missile series emphasized modularity in design to make upgrading the missiles easier as technology developed.

SM-2 Block II

The Block II upgraded the original SM-2 interceptor with a signal processor to harden the system against electronic warfare systems. It also featured an upgraded fuse and focused-blast fragment to the warhead to improve the missile’s capacity to intercept smaller, harder targets. The Block II also featured new propulsion systems for higher velocities and better maneuverability allowing it to effectively integrate more radar data for accuracy.

SM-2 Block III

The currently deployed Block III series of interceptors have a range of around 90 nautical miles. They measure 15 feet 6 inches in length and 13.5 inches in diameter and weigh around 1,558 pounds. The Block III upgrades focused on developing an advanced capability against lower altitude targets and entered service in 1981. The Block IIIA variant, which entered service in 1991, extended the range of the interceptor to even lower altitudes than the standard Block III. 3 The Block IIIB, which entered service in 1998, incorporated the infrared guidance system tested in the Missile Homing Improvement Program (MHIP) to complement the system’s radio frequency terminal homing systems. 4

This dual capability was designed to counter developments in electronic warfare.


    1. United States Navy, “United States Navy Fact File: Standard Missile,” January 12, 2016,
    2. David Ewing and Malcolm Fuller, “SM-2 Block IV,” in IHS Jane’s Strategic Weapons: Naval, (United Kingdom: IHS Global 2016-17).
    3. Ibid.
    4. Eric Heginbotham, “The U.S.-China Military Scorecard: Forces, Geography, and the Evolving Balance of Power 1996-2017,” RAND Corp., 2015,, Santa Monica, California: RAND Corporation.
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Missile Defense Project, "Standard Missile-2 Block II/III," Missile Threat, Center for Strategic and International Studies, April 14, 2016, last modified June 24, 2021,