Serbia Almost Bought Russian S-400 Missile Systems: What It Would Have Meant For NATO and Why It Stopped

The direction of Serbia’s military modernisation efforts has long been an outstanding security question in the European theatre, with the country’s history in the late 1990s of a major war with the NATO alliance and ongoing standoff with the Western-backed Kosovo enclave contrasting with its aspiration to join the European Union and the significant influence which the EU has gained over its economy. Serbia stands out in Europe as one of just two countries alongside Belarus which has maintained security ties with Russia into the 21st century while refraining from moving towards operating a NATO-standard military as countries across the former Warsaw Pact, former Yugoslavia and even multiple Soviet successor states have done. Nevertheless public sentiment in support of Russia in particular, and a history of close security cooperation and joint exercises with Russia and Belarus, has been tempered by Belgrade’s susceptibility to Western pressure. While Serbia has continued to modernise its ground forces with Russian equipment, including second hand T-72MS tanks, the question of its combat aviation and air defences has been particularly sensitive due to the country’s recent historical memory of intensive bombardment by NATO – as well as the Western world’s memory of having to engage Serbian defences and taken losses in the process including two stealth fighters. 

Serbia began to modernise its air defences in the late 2010s with acquisitions MiG-29 fighters which were supplied as aid by both Russia and Belarus, followed by Russian Pantsir-S short range air defence combat vehicles delivered in 2020.  The MiGs were modernised to the MiG-29SE standard, and alongside airframes acquired from the Soviet Union by Yugoslavia in the 1980s brought the fleet up to 14 aircraft. With Serbian combat aviation considered unlikely to pose a serious challenge in the case of a future conflict over Kosovo due to its very small size, its ability to asymmetrically defend its airspace using mobile ground based air defence systems became a particularly important question. It was thus highly significant that Serbia was reported to be considering acquiring the most capable system fielded by the Russian Air Force, the S-400, with speculation of a possible acquisition culminating in the unprecedented deployment of Russian S-400s in October 2019 for exercises on Serbian territory. The S-400 forms the backbone of Russian and Belarusian air defence capabilities, and over 60 regiments are fielded in the Russian Air Force alone with production sufficient to equip several battalions per year. 

S-400s were deployed at Batajnica base outside the Serbian capital Belgrade for the Slavic Shield live-fire exercises in 2019, which the Serbian Defence Ministry reported involved ”use of a joint [combat] group…in defending… against enemy reconnaissance and offensive actions.” The ministry further added that such air defence drills would be held on a regular basis, with the drills focused on increasing interoperability of Russian and Serbian aerial warfare assets. The deployment followed a visit by Russian President Vladimir Putin to Belgrade in January that year. Those exercises saw 14 Serbian aircraft simulate an adversaries, with all of them shot down within three minutes by the S-400 system which fired 26 missiles to achieve this – below the standard two missiles fired against each target. With the S-400 designed to engage advanced fifth generation aircraft, it has long been reported to provide overwhelming superiority against fourth generation fighters such as MiG-29s. During the exercises Serbian President Aleksandar Vucic examined the S-400s and expressed his country’s intentions to acquire the systems should the funding become available.

The S-400 was considered optimal for Serbia’s defence needs, as well as for those of Russia, due to its combination of a high combat potency and very low lifetime operational costs compared to a comparable air defence capability provided by aircraft. This was due to its far lower operational costs and maintenance needs. The system’s very high mobility and compactness also made it a far greater challenge to neutralise compared to fighter aircraft requiring fixed airfields to operate, although the MiG-29s Serbia does operate are among the best fighters in the world for using makeshift ‘guerrilla airfields’ with little preparation. S-400s use multiple radars operating in complementary wavebands to provide a very high degree of situational awareness including against stealth targets, and were developed with engagements against stealth aircraft such as F-22 fighters and B-2 bombers in mind. The system deploys over half a dozen classes of complementary surface to air missiles including the 40N6 with a 400km range – approximately double that of comparable Western air defence assets. The systems would thus have been a game changer for Serbia’s defence needs.

Serbia’s defence budget of approximately $1.1 billion made acquiring S-400s challenging, with a single regiment costing approximately $500 million which would have consumed the country’s entire acquisitions budget for several years. Serbian authorities were thus widely reported in the late 2010s to be considering buying a regiment on a long term credit agreement with Russia. Where the issue of cost could have been circumvented, however, pressure from the European Union leveraging Belgrade’s intentions to accede to the bloc, and threats from the United States to impose economic sanctions, between them deterred the country from going through with a deal. Shortly after President Vucic stated Belgrade’s intentions to acquire S-400s U.S. Special Representative for the Western Balkans Matthew Palmer warned that the response from Washington would be sanctions, with the U.S. from 2017 threatening sanctions on all major clients for Russian military hardware under the Countering American Adversaries Through Sanctions Act (CAATSA). Apparent in response, Vucic stated on November 6 2019 that his government did not intend to purchase the systems. 

While a primary purpose of CAATSA was to deny the Russian defence sector revenues and expand market shares for Western defence producers, there were also key strategic reasons to prevent Serbia from enhancing its air defence network with Russian-supplied assets. Unlike Turkey which also acquired the S-400, Serbia’s interoperability with Russian forces and use of a fully compatible air defence network meant S-400s in Southeastern Europe could be used to provide targeting data and otherwise increase the situational awareness of the Russian Air force, with the system’s 600km detection range making this particularly significant. This was aside from the fact that it would constrain Western options for military options against Serbia itself should tensions rise over Kosovo or other issues. 

While confirming that Serbia would not acquire S-400s, Vucic elaborated regarding the system’s benefits and what he referred to as “an impressive weapon”: “You know, when you have such a weapon, no one would attack you. Neither US nor any other pilots fly where S-400s are operational: Israeli pilots do not fly either over Turkey or Syria, except for the Golan Heights. We have aviation, which the strongest than ever before. We will be strengthening the air defences with Pantsir systems and other things, which are not on the sanctions list.” Serbia continued to face considerable pressure from the West to avoid acquisitions of air defence assets from countries which were not in NATO or NATO aligned, but ultimately despite considerable American and European criticism purchased the HQ-22 system from China in late 2020. These were delivered by Chinese Y-20 heavy transports in April 2022, with some reports speculating that the delivery schedule had been accelerated to bolster Belgrade at at time of high tensions during the Russian-Ukrainian War.

The HQ-22 did not represent a Chinese equivalent to the S-400, being a shorter ranged system that placed greater emphasis on mobility, but it was still a highly potent asset with electronics and sensors on par if not ahead in terms of sophistication. While it did not give the Serbian Air Force the same level of situational awareness against stealth aircraft or hypersonic missiles, or the ability to engage aircraft well beyond Serbian airspace as the S-400 did, its acquisition still revolutionised the country’s aerial warfare capabilities making it by far the most outstanding asset in the air force. Its acquisition potentially also allowed it to serve as a highly complementary asset to the S-400 should political circumstances change and the longer ranged system eventually be acquired. Serbia served as an example of one of multiple states which since the 1990s have been swayed by threats of Western political and economic responses to avoid acquiring high profile weapons systems from Russia, with other examples including  South Korea’s decision not to acquire S-300 air defence systems or MiG-29 fighters in the 1990s, Thailand’s decision not to acquire T-90 tanks in the 2000s, and an Indonesian order for Su-35 fighters in the 2010s being terminated, among dozens of other cases.