The UAV Threat as a Catalyst for NATO’s Return to Gun-Based Air Defense
Unmanned aerial vehicles (UAVs) have become one of the most significant factors in current conflicts. Their mass deployment in Ukraine, the Middle East, and Africa shows that the ability to saturate an opponent's "missile" air defense with cheap and numerous targets fundamentally changes the rules of combat. Modern missile air defense systems, designed to destroy high-value air assets, often prove to be financially unsustainable and tactically ineffective when confronted with inexpensive drones. This has brought back into play assets that have been relegated to storage or completely decommissioned in many NATO armies in recent decades—gun-based air defense systems.
Despite the rediscovery of the importance of surface-to-air defense in recent years, the current state of the Alliance's armaments is uneven and, in many cases, reflects the legacy of the Cold War rather than a well-thought-out modernisation policy. Most member states can be divided into four groups according to whether and what systems they have at their disposal.
The largest group consists of countries that have completely phased out their cannon-based systems. These include Albania, Belgium, the Czech Republic, Denmark, France, Germany, Hungary, Ireland, Iceland, Italy, Lithuania, Luxembourg, Montenegro, the Netherlands, Norway, Slovenia, the United Kingdom and Canada. These armies rely mainly on short- and medium-range missiles (if they have any air defense at all) or on allied support. In many cases, cannon-type air defense was considered obsolete and ineffective, leading to its decommissioning during the 1990s and early 21st century.
Some countries, especially those on the eastern flank of the alliance, still rely on Soviet-era technology. Bulgaria maintains ZSU-23-4 Shilka, towed ZU-23-2 and 57mm S-60 cannons. Croatia operates BOV-3 self-propelled vehicles armed with 20mm cannons. Estonia has towed 23mm ZU-23-2s. Although these systems are capable of countering UAVs, they are technologically outdated and have significantly limited ability to integrate into modern command and control systems.
Another group of countries operates Western cannons of varying ages and modernisation levels. Latvia has 40 mm Bofors L/70 cannons in its arsenal, North Macedonia uses older 40 mm L/60 variants, and Portugal has 20 mm Rh 202 cannons. Slovakia is an exception, operating the modern C-RAM MANTIS system with 35mm cannons. Spain still has a large arsenal of 35mm Oerlikon GDF-005/007. Sweden relies on Lvkv 90 self-propelled systems with 40mm cannons. Turkey operates an extensive arsenal, which includes Korkut self-propelled systems with 35 mm cannons and a large number of towed weapons of various calibers. Although the USA has decommissioned most of its cannon air defense systems, it maintains some weapons as part of the M-LIDS and C-RAM Phalanx LPWS systems.
Some member states combine Soviet and Western weapons. Finland has more than four hundred 23mm ZU-23-2 (ItK 61/95) guns and also operates 35mm Oerlikon GDF-005 (ItK 88) guns and Marksman self-propelled systems on Leopard 2 chassis. Greece has a wide range of weapons: 20mm Rh 202, 23mm ZU-23-2, 30mm Artemis-30 and 35mm Oerlikons with the Skyguard system. Poland combines Soviet ZU-23-2s with domestic modernisation (ZUR-23-2KG Jodek-G) and new Pilica systems, which combine cannons with portable anti-aircraft missiles. Romania has both German Gepards and Swiss 35mm Oerlikons in its arsenal, alongside older 57mm S-60 cannons.
In terms of availability and modernity, cannon-based air defense within NATO is significantly unbalanced. While some member states have retained their capabilities, often in significant numbers (Turkey, Greece, Poland, Spain), most of the Alliance has completely lost its cannon air defense. These differences are of fundamental importance in the context of the current UAV threat: countries without cannon air defense must rely on missile systems, whose deployment against cheap drones is economically unsustainable.
Trends and modernization projects
The Federal Republic of Germany is one of the countries that decommissioned most of its cannon systems after 1990. However, experience with the deployment of Gepard self-propelled vehicles in Ukraine has shown that even older technology can be effective against Shahed-136 UAVs. As a result, there has been renewed interest in modern solutions: Rheinmetall is developing the Skyranger 30/35 system, which combines a rapid-fire cannon with programmable ammunition, advanced sensors, and the possibility of integration into a multi-layered air defense system. Germany is considering purchasing it for both its own army and for export.
Poland has decided to strengthen its air defense by combining traditional means with new concepts. The basis is the Pilica system, which combines 23mm cannons with Piorun portable anti-aircraft missiles. In the modernized Pilica+ version, the system is supplemented with the ability to cooperate with short- and medium-range missile systems, creating a comprehensive multi-layered defense against UAVs and other threats. The U.S. Army has long relied almost exclusively on missiles. However, in response to the growing threat of UAVs, the M-SHORAD program was created, which uses a 30mm cannon with programmable ammunition and Stinger anti-aircraft missiles on a Stryker chassis.
Turkey is one of the few NATO countries that has continuously invested in cannon-based air defense systems. The Korkut system, based on a pair of 35mm cannons with modern ammunition, is a modern self-propelled weapon capable of effectively countering UAVs, helicopters, and certain types of missiles. Ankara also maintains an extensive arsenal of towed weapons of various calibers, which gives it flexibility and the ability to counter low-cost threats on a mass scale. The Slovak Republic has become one of the few countries to have the most advanced MANTIS system at its disposal. This system uses 35mm cannons with programmable AHEAD ammunition and is primarily designed to protect strategic objects against rockets, mortar and artillery ammunition. However, thanks to its rate of fire and accuracy, it is also an effective weapon against UAVs.
The Nordic countries have traditionally retained a larger portion of their cannon air defense than most of their alliance partners. Sweden operates Lvkv 90 self-propelled systems with 40mm cannons, while Finland maintains an extensive arsenal of 23mm and 35mm weapons and is modernizing them as part of its command and control systems. The experience of proximity to Russia and the emphasis on territorial defense contribute to the fact that the countries in this region have not underestimated the importance of barrel weapons. The above-mentioned modernization programs reveal trends in the renaissance of cannon air defense: 1) programmable ammunition capable of creating clouds of sub-projectiles against small UAVs, 2) integration into C4ISR systems, enabling rapid response and networked defense, 3) modularity – cannon turrets can be installed on various chassis.
Doctrinal and technological arguments for a renaissance
The renewed interest in surface-to-air defense within NATO is not accidental. It stems from changes in the security environment and technological developments that have called into question the unilateral reliance on missile systems. Short-range missile systems (VSHORAD/SHORAD) are effective but also costly. Stinger or Mistral missiles cost tens of thousands of dollars, while improvised or mass-produced Shahed-136 UAVs cost thousands. This disproportion leads to so-called economic asymmetry, where an attacker can cheaply deplete the defender's stockpile of expensive missiles. In contrast, the price of a single cannon shell with programmable ammunition is significantly lower, allowing for a more sustainable defense. Another factor is capacity. A vehicle equipped with a cannon can carry hundreds to thousands of rounds of ammunition, while a typical launch system has only a few missiles. This means that cannon systems are more suitable for repelling swarm attacks by UAVs, where the ability to repeatedly and quickly engage a large number of targets is crucial.
Cannon systems have an advantage when firing at low-flying and maneuvering targets that can evade detection by radars designed for higher flight levels. UAVs often fly at low altitudes, use terrain obstacles, and approach from unexpected directions. Short reaction times and high rates of fire increase the probability of a successful hit. Modern cannon systems can be deployed not only against UAVs, but also against helicopters, fighter aircraft, and lightly armored ground targets. This makes them multipurpose weapons that are particularly attractive to smaller armies with limited budgets. While in the post-1990 period NATO emphasized expeditionary operations and the suppression of asymmetric threats, the current doctrine once again emphasizes territorial defense and preparation for high-intensity conflict. This includes the need to protect troops on the battlefield and deep rear areas from swarm attacks by UAVs, low-cost flat-trajectory missiles, or artillery ammunition. Cannon air defense thus finds its place in a multi-layered defense architecture as the "first line" against low-cost and numerous threats. Cannon air defense is not a competitor but a complement to missile systems and, more recently, laser weapons. The trend is toward building hybrid systems, where the individual layers form an interconnected whole.
