Russia's fearsome S-400 air-defense missiles are getting unexpected missions as Moscow struggles in Ukraine

• Russia's S-400 is a highly regarded weapon designed to intercept a variety of aircraft and missiles.
• In Ukraine, expensive S-400 interceptors are being used against rocket artillery and ground targets.

Russia's S-400 advanced air-defense system is designed to shoot down aircraft and missiles and long ranges and high altitudes. But in Ukraine, Moscow has pressed its S-400s into service to intercept US-made HIMARS rockets or, more bizarrely, to bombard Ukrainian cities.

Moscow is portraying tactic this as proof that Ukraine's air force is so weak that Russian forces can afford to waste expensive anti-aircraft missiles on secondary missions. The more likely reason for it is that desperation and frustration are driving the Kremlin to use every weapon it has, no matter how inappropriate it is for the task.

The S-400 Triumf is a mobile, long-range surface-to-air system that is considered Russia's equivalent to the US's Patriot missile. S-400 interceptors have an estimated range of about 250 miles and a reported speed of Mach 15, and Russia claims the weapon is effective against aircraft, cruise and ballistic missiles, and drones.

There have been reports of S-400s deployed to the Donbas region to intercept the HIMARS rockets that Ukraine has used with devastating effect since last summer. To some degree, this is not unusual. Modern SAMs are designed to intercept a variety of missiles and aircraft. Ukraine has used the S-300 — predecessor to the S-400 — and the American-made Patriot to intercept Kalibr cruise missiles and even Kinzhal hypersonic weapons.

The problem is that the Guided Multiple Launch Rocket System munitions that HIMARS fires aren't missiles but GPS-guided artillery rockets with a range of about 50 miles, much shorter than cruise and ballistic missiles.

Launched at targets relatively close to the front line, GMLRS has a different trajectory and a much shorter flight time in which an air-defense system can intercept it.

"You're not going to detect it over the horizon," Ian Williams, deputy director of the Missile Defense Project at the Center for Strategic and International Studies, told Insider. "It doesn't go into space like a ballistic missile does. I think the biggest challenge would be the short engagement time."

Williams believes that the S-400 could intercept a HIMARS rocket but not very easily. A more suitable system to destroy HIMARS rockets would be Israel's Iron Dome, which has frequently intercepted small rockets and even mortar shells. (Ukraine has asked Israel for Iron Dome, but Israel has declined, likely in part over concern about Israeli relations with Russia.)

"Iron Dome is more optimized for that kind of target," Williams said. "The Tamir interceptor is pretty maneuverable. The radars are more attuned to detecting smaller, low-altitude targets."

A Tamir missile also costs less than $150,000, while a big SAM costs closer to a million dollars each.

While using S-400s against HIMARS suggests Russia is struggling with air defense, what really indicates the Kremlin's desperation is its use of S-400 and S-300 interceptors for surface-to-surface bombardment of Ukrainian cities. A 400-pound warhead may be devastating against an aircraft or another missile, but it is actually small compared to the 2,000-pound warhead on a cruise missile like the Russian Kh-22.

"They can only be a terror weapon because they're very inaccurate in a surface-to-surface role," Williams said of repurposed interceptors.

Moscow has resorted to bombarding Ukrainian infrastructure in the hopes of keeping pressure on Kyiv. That aerial campaign has taxed Russian stockpiles, leading Moscow to use older cruise and ballistic missiles as well as drones. In that context, Moscow may view the wrong missile as better than no missile at all.

Ukrainian and British intelligence concluded in 2022 that Russia's intense bombardment of Ukrainian cities and infrastructure was depleting its missile supply. Some analysts disagree with this assessment, but munitions shortages are a concern for both sides.

Leaked US intelligence assessments compiled in February indicated that Ukraine could deplete its air-defense munitions by May, though Western countries have scrambled to replenish those stockpiles. The problem may be more acute for Russia, which faces extensive Western sanctions on critical military hardware.

This isn't the first time surface-to-air missiles have been used for other purposes. Egyptian forces fired them at Israeli tanks during the 1973 Arab–Israeli War. But anti-aircraft missiles aren't meant to fired at tanks or cities. For Russia's military, which has long touted its tactics and technology, having to misuse S-400s is a sign things aren't going well.

Michael Peck is a defense writer whose work has appeared in Forbes, Defense News, Foreign Policy magazine, and other publications. He holds a master's in political science. Follow him on Twitter and LinkedIn.