Russia and Ukraine are both beefing up their air defenses ahead of another winter of bombardment

• Ahead of another winter of war, Russia and Ukraine are bolstering their air-defense arsenals.
• Ukraine and its foreign partners are scrambling to field new and improvised air-defense weaponry.
• The Russian military appears to be sacrificing elsewhere to reinforce its air defenses in Ukraine.

As the start of the second winter of their renewed war looms, both Ukraine and Russia are trying to beef up their air defenses.

For Kyiv, effective defenses could decide whether Ukrainians freeze during another campaign of Russian missile and drone attacks on Ukraine's cities and critical infrastructure. For Russia, the ability to knock down Ukraine's drones and Western-supplied missiles will be crucial to whether Russian troops can maneuver and be resupplied during upcoming ground operations.

For both sides, capable air-defense systems are vital for countering the constant presence of surveillance and explosive drones over the battlefield, where they can paralyze military operations.

Despite Russia's attempts to suppress them at the start of the war, Ukraine's air-defense forces have proven remarkably effective at using a mix of Soviet-era systems, such as the S-300 and Buk anti-aircraft missiles, as well as Western weapons such as US-made Patriot missiles and German-built Gepard anti-aircraft guns.

But after two years of incessant barrages by Russian missiles and waves of Russian- and Iranian-made drones, Ukraine is running low on air-defense missiles and cannon ammunition.

The US and European countries are scrambling to boost defense production to resupply Ukraine, but as their output ramps up slowly, they are dipping deep into domestic stockpiles to support Kyiv while scouring the world for missiles and ammunition compatible with Ukraine's Soviet-era equipment.

To meet their needs with what they have right now, the US and Ukraine have turned to a quick fix: the "FrankenSAM," which mates Western-built missiles with Soviet-designed launchers and radars. America has ample stocks of AIM-7 and AIM-9M missiles, as well as the RIM-7 naval variant, that it has already supplied to Ukraine for air defense.

Only Russia still builds missiles for the Soviet-designed air-defense systems Ukraine is using, and Kyiv and its backers now face "a basic structural problem" after two years of "buying up all the missiles available around the world" for those weapons, according to Michael Kofman, an American expert on the Russian military at the Carnegie Endowment for International Peace.

FrankenSAM may be a solution to that munitions shortage, Kofman said on a November 6 episode of the War on the Rocks podcast.

The FrankenSAM effort "seems to have yielded systems that we can supply," Kofman said. "It may not be in high numbers that we can produce per month but will allow us to provide a modified version of a Ukrainian Buk or some other systems that will fire our missiles."

Russian missiles and drones have been a persistent menace to Ukrainian troops and civilians, but Russia has air-defense problems of its own.

Since early in the war, Ukraine has employed domestically developed and foreign-provided military-grade drones as well as commercial drones modified to carry munitions. Its forces have used large drones armed with missiles and small quadcopters to strike big targets like Russian tanks and small, cheap first-person-view drones to target individual Russian soldiers.

Ukrainian drones have also struck deep inside Russia, hitting bases and major cities, including Moscow. Those strikes have caused minimal damage but are nonetheless embarrassing for a regime that bases its claim to power on being able to defend Russians.

Perhaps the biggest threat is Ukraine's long-range munitions, such as US-made ATACMS and HIMARS rockets and British-made Storm Shadow cruise missiles. These weapons have been responsible for devastating strikes against Russian bases, supply depots, and infrastructure, such as the bridges that allow supplies to reach the garrison in Crimea.

Russia has an extensive air-defense arsenal with which it has maintained coverage over its cities, borders, and strategically valuable territory like the Baltic Sea exclave of Kaliningrad. Those weapons, including its most advanced surface-to-air system, the S-400, have also been deployed to Ukraine.

In recent months, several S-400s have been destroyed in Ukrainian attacks. Analysis by the British Defence Ministry earlier this month indicated that Moscow would "highly likely" have to move other air-defense weapons to Ukraine, showing how the war "continues to overextend Russia's military and strains its ability to retain baseline defences across its vast area."

Public flight-tracking information compiled by open-source research outlet Bellingcat indicates that such moves were already underway in late October, with military cargo planes transporting S-400 batteries out of Kaliningrad in what the Defence Ministry this week called "exceptional Russian air-transport movements."

The destination of those S-400s is unclear, but given that Russia has devoted enormous resources to air defense of "the Motherland" since the 1930s, stripping important locations like Kaliningrad of anti-aircraft weapons is a sign of desperation.

That Russia's military "appears willing to accept additional risk" at that strategically important outpost "highlights the overstretch the war has caused for some of Russia's key, modern capabilities," the Defence Ministry said this week.

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.