The Avenger Air Defense System provides short-range air defense on the go -- whether it is rolling into combat in Ukraine or flanking the Pentagon in Arlington, Virginia.

The highly mobile US-made Avenger system is a short-range defense weapon that can shoot on the move, is completely automated and is capable at day or at night. It can stand alone or work with integrated air and missile defense systems.

The US Army and US Marine Corps have used the Avenger for mobile, short-range defense to protect ground units.

The self-propelled, surface-to-air missile system can defend against cruise missiles, unmanned aerial vehicles (UAVs), low-flying fixed wing aircraft or helicopters.

Its basic configuration has a gyro-stabilized air defense turret mounted on a modified heavy four-wheel-drive military truck.

The Avenger turret can be mounted on a variety of vehicles, including Mine-Resistant Ambush Protected vehicles, or used as a stand-alone, fixed-mounted weapon station, according to its manufacturer, Boeing.

Four decades of mobile defense

Boeing developed the Avenger in the 1980s for the US armed forces. It was created as a mobile unit that could be used on the ground or while on the move to protect other ground units. The Defense Acquisition Board approved the Avenger system for full-scale production in 1990.

When it was first tested in 1984, it made a direct hit against Stinger missiles while the Avenger was moving 20 miles per hour (32km/hour). It had success in other challenging environments in the testing scenario: it made a direct hit at night and a "tactical kill" while being driven in the rain.

The US Army awarded the first production contract for the Avenger in 1987, for 325 units. Since then, Boeing has built more than 1,000 Avenger units for the US military.

About 400 remained in service by 2016. The Avenger is currently used most by the US Army National Guard.

It was successfully deployed in the first Gulf War and in support of NATO operations during the war in Bosnia.

The US Army positioned a network of Avengers loaded with Stinger missiles around the Pentagon and in Washington, DC, in September 2002 for the first anniversary of the September 11 attacks on the Pentagon and in New York City.

It also deployed Avengers in Afghanistan and Iraq, to support the US European Command and to support Ukraine against the Russian invasion.

A specialized system and its ongoing adaptations

The Avenger includes a specialized vehicle: radars, platforms, Stinger missiles and a .50 caliber machine gun, as well as command, control and intelligence system.

A 360-degree rotating turret is mounted on a heavy vehicle chassis. The turret has two missile pods, which hold up to four Stinger missiles each. It is gyro-stabilized so the missile pod can aim while the vehicle is in motion.

A gunner operates inside a firing station between the two missile pods.

Crews can also operate the weapon system from a remote control unit up to 50 meters away to try to avoid enemy direct fire.

Boeing and the Army have been at work on upgrades and adaptations to the Avenger system.

The Avenger was developed as an air defense system, but Boeing has explored more ground defense capabilities to give it more versatility. In 2011, the Army evaluated the feasibility of this idea with a test launch of an AGM-114 Hellfire missile from a modified Avenger weapon.

In another test in April 2017, the Avenger fired Stingers at two UAVs -- the missile's first interception of a UAV target.

Boeing also developed a Laser Avenger, a laser system mounted on the Avenger. The lasers can shoot down small UAVs mid-flight with an infrared laser that is invisible to the naked eye.

Stinger missiles

In most cases, the Avenger is equipped with the Stinger missile, a relatively lightweight, self-contained air defense system. It is a passive surface-to-air missile.

The Stinger has more than 270 fixed and rotary-wing intercepts to its credit, according to its manufacturer, RTX (formerly Raytheon).

Stinger can be shoulder fired by an operator or fired from an Avenger or another mobile defense unit, the M6 Linebacker. It also can be used by airborne troops or deployed straight off a rack on a Humvee.

The Stinger missile improved on the previous FIM-43 Redeye system, because the Stinger can acquire a target from head on, which gives it more time to acquire and destroy a target.

It is launched by a small ejection motor that pushes it a safe distance away from the operator, where its solid-fuel sustainers can then engage and accelerate it to the target. It has an impact fuze and self-destruct timer.

Another variation of the missile uses a proximity fuze that makes it more lethal against small targets.