Kyiv’s Request for S-300 Air-Defense Systems, and the Looming Battle for Donbas

As March drew to a close, Moscow recalibrated its maximalist war aims in Ukraine, officially designating the “special military operation” as now aimed primarily at “liberating” the entire Donbas region. The demonstrated regrouping of Russia’s forces in the vicinity of Kyiv and Chernihiv is supposed to presage a much wider and deeper Russian assault on the Ukrainian “Joint Forces Operation” (JFO) military units, which had been engaged along the line of control in Donetsk and Luhansk oblasts until February 24, 2022, when the Kremlin launched its massive re-invasion of the country. A critical element in this looming battle for Donbas is likely to be the broader systemic use of Russian airpower, which until now has not featured on a scale commensurate with a large-scale war. The reluctance of the Aerospace Forces (Vozdushno Kosmicheskikh Sil—VKS) to engage at this level or to send long-range strategic aviation to target the JFO, stems from the threat posed by Ukraine’s air defenses and, specifically, its Soviet-developed S-300PT and S-300PS surface-to-air missile (SAM) systems (Mil.ru, RBC, March 25).

Ukraine’s inventory of S-300 variants has been targeted and degraded since Russia massively escalated the war beyond Donbas on February 24. This has driven calls by Kyiv to the North Atlantic Treaty Organization (NATO) and its members to resupply these systems by sourcing them from Bulgaria or Slovakia on a bilateral basis. On the eve of the re-invasion, Ukraine fielded both S-300PT and S-300PS SAM systems. However, these have been targeted by Russian forces since the outset of the conflict, which has reportedly resulted in the destruction of 17 battalion sets of these air-defense assets. Twelve launchers for the S-300PT (5P851A) were destroyed, with an additional three S-300PS launchers (5P85D) destroyed; moreover, three 5P85S “master” S-300PS launchers were destroyed and another three captured. So in total, 17 Ukrainian S-300 launchers have been destroyed and 3 captured, according to open-source analysis (Oryx.com, accessed, March 31). Successful Russian strikes against Ukraine’s S-300 systems have been cataloged through video and photographic evidence uploaded on social media, with examples such as the destruction of the S-300PS system in Svatove on March 17, or the Russian defense ministry’s footage of a destroyed S-300PT system on March 30 (T.me/mod_russia_en, March 30; T.me/ChDambiev, March 17).

The Russian Ministry of Defense contends its Armed Forces have achieved air supremacy in Ukraine, offering doubtlessly exaggerated figures to support the claim: destroying 123 aircraft out of Ukraine’s 152 operational platforms, 77 of 149 helicopters and, in terms of long- and medium-range air defenses, 152 Ukrainian systems destroyed out of 180 total (Krasnaya Zvezda, March 30). During the defense ministry’s briefing on March 31, Moscow professed to have eliminated an S-300 system, in addition to four command posts, an ammunition depot and four large fuel bases in Dnepropetrovsk, Lisichansk, Novomoskovsk and Chuguev, to “significantly complicate” the supply of Ukrainian forces in Donbas (Novostivolograda.ru, March 31).

Moscow’s reduction of stated war aims to focus on Donbas appear to mark an abandonment of its much more ambitious regime change and occupation goals at the start of the war. In Donbas, most of the gains made are in Luhansk region, with Russian forces constantly shelling the line of contact. The Ukrainian JFO forces, among the country’s most elite and battle-hardened military units over the past eight years, have assumed positions to conduct positional defense, which could prove costly for the Russian Ground Forces to attack. Envelopment of the JFO from the northern and southern axes seems the most likely operational approach, though with no guarantee of success; the ensuing battle for Donbas is expected to be extremely tough fought. This is why the option of greater involvement of the VKS, particularly to attrit these in combination with ground-based fires—which could conceivably involve the use of VKS long-range bombers—must be taken seriously (Mil.ru, RBC, March 25).

The aim to seize the entire territory of Donbas, in turn, puts pressure on Russia’s Armed Forces to avoid the catalog of mistakes and operational ineptitude that has marked the majority of the near-disastrous invasion to date. The lackluster performance also extends to the sporadic and minimal use of Russian airpower. If the coming battle for Donbas is to preclude replicating these failed approaches, the VKS will have to engage on a much wider and systematic scale; thus, the potential role of Ukraine’s S-300 systems is a key aspect in the country’s capacity to withstand a better executed Russian air-ground assault on Donbas. While Russian claims of success against long- and medium-range Ukrainian air defenses are likely inflated, the degradation of the S-300s is further confirmed by Kyiv’s growing calls for NATO members to supply S-300 replacements. In Washington, the Joseph Biden administration is considering sourcing options from Slovakia or Bulgaria, carefully weighting those against its fears of allowing the conflict to escalate into a wider European war (UNIAN, March 30).

United States Secretary of Defense Lloyd Austin has explored the issue in bilateral talks, with Slovakia emerging as the most likely source for the export of the Soviet/Russian S-300 systems to Ukraine. However, besides the political questions linked to this option, there are additional potential military-technical issues at play quite apart from what such suppliers might receive in return from the US. In the case of Slovakia, the S-300PMU remains in service. The main issue with it is the limited number of serviceable 55V55R missiles delivered in 1990. This compelled the Slovak Armed Forces to reduce the standard number of missiles from four to two in operating the complex. Nonetheless, despite the degradation of the Ukrainian S-300 systems, they clearly have well-trained and experienced air-defense personnel to exploit this asset. But the availability of 55V55R missiles in the Ukrainian military inventory is an open question. In the case of Bulgaria, there are two S-300P battalions in service with ten launchers, though their condition remains unclear. Greece also possesses the S-300PMU1 in significant quantities—32 launchers and up to 175 missiles—although Athens is much less likely to agree to aid Ukraine in this sensitive area; it would also require time to retrain Ukrainian personnel in this variant’s use (Izvestia, March 18).

In the event of the transfer of Slovak and/or Bulgarian S-300 systems to Ukraine, at best, this would yield three battalions. The general technical condition of these systems remains unclear. Finally, given the Russian targeting of Ukrainian S-300 systems in the war, their transfer across the borders of Romania, Poland or Slovakia will incentivize Russia to try to attack these weapons upon entry into Ukraine (Izvestia, March 18). Yet if these are kept mobile and concealed while stationary, it may enhance their survivability. The necessity of providing adequate long-range air defenses to Ukraine may sway the argument.