The US Army faces a threat from the air that the Air Force can’t stop. Here’s how it’s trying to defend itself

• The devastating use of drones during the recent war between Armenia and Azerbaijan highlighted how modern aerial threats, such as drones, have evolved in recent years.
• This is a particular problem for the US Army, which shrunk its air-defense arsenal after the Cold War and is now trying to rebuild it to counter new and emerging threats.
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The recent six-week war between Armenia and Azerbaijan over the disputed Karabakh region left nearly 6,000 troops and civilians from both sides dead and hundreds of pieces of military hardware destroyed.

Azeri drones caused much of that destruction. Hours of drone footage showed devastating precision strikes against Armenian targets and reignited debate about the future of the tank.

The US Army was not part of the conflict, but it was a reminder of an inconvenient truth that the service has known for at least a decade: Its anti-air (AA) defenses are severely lacking.

The air-defense arsenal

The Soviet Union’s collapse diminished the prospect of great-power war. With a lack of serious air threats, the Army got rid of many of its air-defense units and directed their resources elsewhere.

As a result, its air-defense arsenal, especially ground-based AA platforms like short-range air defense (SHORAD) systems, is now much smaller.

Three of the Army's primary ground-based AA systems - the MIM-23 Hawk, the MIM-72 Chaparral, and the M163 VADS - were retired between 1991 and 1998. From 2004 to 2018, the US Army reduced the number of SHORAD battalions from 26 to nine.

In 2004, the last armored AA system, the M6 Linebacker, was phased out. Today, the Army's only air-defense systems are the shoulder-launched Stinger man-portable air-defense (MANPAD) system, the AN/TWQ-1 Avenger, the MIM-104 Patriot, and the Terminal High Altitude Area Defense (THAAD) system.

The Stinger and Avenger - the Avenger is just a wheeled launch system with eight Stingers - are designed to engage aircraft up to about 10,000 feet. The Patriot and THAAD are designed to intercept aircraft and missiles at up to 73,000 feet for the Patriot and up to 93 miles for THAAD.

Faster, cheaper threats

US Air Force fighter jets have been tasked with eliminating threats those systems can't hit - especially other enemy fighters and bombers. They've done well against the largely inferior air forces of Iraq, Libya, Syria, and Yugoslavia, but the threats are changing.

"Our capabilities against adversary aircraft are, in general, very good." Mark Cancian, a senior advisor at the Center for Strategic and International Studies and a former Marine Corps colonel, told Insider.

But the biggest aerial threats of the future are not enemy fighter-bombers. "The two big ones are drones and cruise missiles," Cancian said, adding that "there are very real concerns" about those threats.

In January, Iran launched more than a dozen cruise missiles at two Iraqi bases housing US personnel. None of the missiles were shot down or intercepted, and their impact left more than 100 servicemen with mild traumatic brain injuries.

That was one of several missile and drone attacks across the Middle East in recent years. 

Drones and cruise missiles are smaller, cheaper, and operate at lower altitudes than jets, making it easier for adversaries to use them in large numbers. They can also be very fast - especially cruise missiles - which makes intercepting them with Air Force fighters not only difficult but economically unsustainable.

Like the Air Force, the Army is reluctant to use more sophisticated AA weaponry against such small, inexpensive, and often hard-to-hit targets. Army officials have said that using a $3 million Patriot missile against a drone that costs a few hundred dollars isn't "a good economic exchange ratio."

"The problem with drones is they tend to be very cheap, so there's no point in firing a $100,000 missile at a $1,000 drone," Cancian said. "You really need something else."

Rival investment

While the US has been downgrading its ground-based AA defenses, its rivals have been investing in them heavily - largely because of US airpower dominance.

Alongside larger systems like the S-300 and S-400, Russia has a number of tracked and wheeled AA platforms - most notably the Buk and Tor missile systems, the 2K22 Tunguska, and the Pantsir S-1. In addition to missiles, the Tunguska and Pantsir have 30 mm autocannons capable of hitting low-flying targets. The systems together create a layered defense.

Russia is also developing a new AA artillery system, the Derivatsiya-PVO. Designed specifically to shoot down drones and cruise missiles, the system is armed with a 57 mm main gun capable of firing smart munitions that can explode mid-flight.

Russia claims its AA systems have beaten back dozens of drone attacks on its bases in Syria this year, after first experiencing such attacks in 2018. Russian AA systems do not always triumph over drones and missiles, but Moscow's continuing investment on top of systems it already has give it an advantage.

China also has a number of ground-based AA defenses, most notably the HQ-9 medium-to-long-range AA system, as well as the Type 95 and Type 09 self-propelled AA artillery systems.

Layered defense

This is not to say that the US Army isn't addressing what has been called a "modern-day missile gap." In fact, the opposite is the case.

The Army's Asymmetric Warfare Group began developing counter-drone training, technology, and tactics in response to ISIS's use of small drones, and while the AWG is being deactivated, air and missile defense was among the Army's top priorities in 2020 and is expected to remain so for the next four years.

The Army has begun fielding a new interim system, the IM-SHORAD Stryker, for its immediate AA needs. The Indirect Fire Protection Capability (IFPC) system, armed with the most recent AIM-9X Sidewinder missile, is also expected to enter service in the next few years. Soldiers in Texas are testing Israel's Iron Dome system, developed with US technology, as an interim cruise-missile defense.

The Army is also looking at long-term solutions like rail guns, directed-energy weapons and jamming technology. Those will take longer to develop and field, but it is clear that the Army is prioritizing air and missile defense and intends to counter future air threats with a variety of systems.

"This is not a single technology or single set of technologies that will be fielded." Cancian said. "It's going to be a series of technologies."

Those systems will have to work together to stop what the Army sees coming.

"Where the Army's going to is a layered defense," Gen. James McConville, the Army's top officer, told lawmakers in March. "We want to be able to tie every sensor to shooter."