MIM-104 Patriot: the US Army's mobile air defense system

The MIM-104 Patriot is a mobile, ground-based air defense missile system fielded by the US Army since its first battalion was activated in May 1982. RTX, formerly Raytheon, is the prime contractor for the system, while Lockheed Martin builds the PAC-3 interceptor missiles². The name is an acronym for Phased Array Tracking Radar to Intercept on Target. Beyond the United States, 19 countries field or are authorized to field the system¹, among them Germany, Japan, Israel, Saudi Arabia, South Korea and Poland.

Design and development

Patriot grew out of a 1960s Army program aimed at high-performance aircraft. A battery’s main sensor is the AN/MPQ-53 phased-array radar, which handles search, detection, tracking and missile guidance for the whole battery. The Congressional Research Service describes the radar as able to track more than 100 targets out to over 100 km. A battery can run in semiautomatic mode, where a human approves each engagement, or in automatic mode; the Army has discontinued automatic mode after friendly-fire incidents¹. The engagement control station, designated AN/MSQ-104, is the system’s only manned component², linked to its launchers by VHF radio or fiber-optic cable.

Specifications

The dimensions and weight below describe the M901 launching station, the trailer-mounted unit that holds and fires the missiles, loaded and mounted on its M860 semi-trailer; Army Recognition gives it as 12.2 m long, 2.6 m wide and 3.9 m high, weighing about 36 tonnes in that state, figures not confirmed by a second source. The launching station has no engine of its own: it is towed by an M983 HEMTT 8x8 tractor with a 445-horsepower diesel, which Army Recognition gives a road speed of 80 km/h³. The only crewed part of a battery is the engagement control station, operated by three soldiers²; a full battery, including its radar, launchers and generators, usually fields between 70 and 90 soldiers in total⁴.

Armament and protection

A PAC-2 interceptor uses a blast-fragmentation warhead of about 90 kg against aircraft, with some capability against tactical ballistic missiles; Army Technology gives the missile a range of 70 km and a ceiling over 24 km². The newer PAC-3 and PAC-3 MSE are smaller, hit-to-kill interceptors built to destroy ballistic and cruise missiles by collision rather than blast, with limited capability against aircraft. A launching station holds four PAC-2 missiles, or up to 16 of the smaller PAC-3 rounds, and can be ready to fire a missile in less than nine seconds¹.

Variants

The baseline MIM-104A entered service in 1982, with the PAC-1 software upgrade, adding limited ballistic-missile capability, following in 1988. The PAC-2 missile, the first optimized against ballistic missiles, reached Army units in 1990, in time for the system’s combat debut. The hit-to-kill PAC-3 missile was first deployed in 1997. The Army is now buying the further-refined PAC-3 MSE, and the Navy reportedly plans to integrate that missile onto Aegis destroyers¹, with initial operational capability targeted for 2028. The Army built 1,106 launching stations in all, of which 483 remained in Army service as of 2010, and had exported more than 250 more to 18 countries⁴.

Operators and service

Patriot’s first combat use came on 18 January 1991, when a US battery engaged what was later found to be a computer glitch; no Scuds were actually fired at Saudi Arabia that day, and the episode was widely misreported as a successful interception. How many Scuds Patriot destroyed over the course of the Gulf War remains disputed among independent analysts. A software error that let one Scud through unopposed killed 28 US soldiers at Dhahran, Saudi Arabia, on 25 February 1991. Saudi Arabia and the United Arab Emirates have used their own Patriot batteries against Houthi missiles fired from Yemen since 2015. Ukraine began receiving Patriot batteries from allied governments in 2023; Kyiv has said its batteries have shot down Russian Su-34 and Su-35 fighters, Mi-8 helicopters and Kinzhal missiles⁴. Washington’s Congressional Research Service counts 19 nations as fielding or authorized to field the system; the Army currently organizes its own batteries into 15 active-component battalions, with three more planned between fiscal years 2029 and 2031¹.

Similar vehicles

Russia’s S-400 was developed as an upgrade of the earlier S-300 series and is mounted on truck transporter-erector-launchers⁵. Israel’s David’s Sling, jointly developed by Rafael Advanced Defense Systems and Raytheon to intercept aircraft, drones, ballistic missiles, rockets and cruise missiles⁶, and the Franco-Italian SAMP/T, which Denmark reportedly picked over Patriot in 2025¹ in part for shorter delivery times, fill a similar medium-to-long-range air and missile defense role among NATO and allied forces.