New Delhi: The fundamental vulnerability in India’s enduring dependence on Russian materiel lies less in evaluating its overall battlefield performance, but more in Moscow’s ability to sustain these capabilities over time – a problem starkly illustrated by the Almaz-Antey ‘Triumf’ S-400 integrated air and missile defence system (IAMDS).By mid-2023, the Indian Air Force (IAF) had commissioned three of the five S-400 regiments it had acquired in 2018 for $5.5 billion and was awaiting delivery of the remaining two. Following the system’s strong performance during Operation Sindoor in May, India had quietly opened negotiations with Russia to procure at leasing five additional S-400s, or possibly the advanced S-500 Prometey/Prometheus IAMDS.Deployed in northern and western India, the three S-400 units had reinforced the country’s multi-layered air-defence network during the four-day conflict with Pakistan, countering a range of aerial threats, mirroring the system’s reported performance in the Ukraine war, where it intercepted the vast majority of munitions fired into Russian airspace.Sustaining India’s current S-400 units faces mounting challengesBut operational success aside, analysts at the Royal United Services Institute (RUSI) in London warned that sustaining India’s current S-400 units – and potentially expanding its inventory – faced mounting challenges. They noted that the system’s manufacturing and maintenance was no longer solely with Russia, but increasingly reliant on China, with interceptor replenishment, radar refurbishment, software updates, and other key components linked to Chinese tooling and supply-chain priorities.Dr Jack Watling, senior research fellow for land warfare at RUSI and a leading analyst of the Russia-Ukraine war, argues that such ‘persistent vulnerabilities,’ compounded by sweeping sanctions on the Russian military-industrial sector, sustained wartime attrition, and diversion of Moscow’s resources to the ongoing conflict, had severely strained the S-400s production and maintenance cycles.In a December research report for RUSI titled Disrupting Russian Air Defence Production: Reclaiming the Sky, Watling maintained that Russia’s integrated air and missile defence architecture – central to protecting its military and including the S-400 – was ‘far more vulnerable than generally understood. Its production, he noted, relied heavily on foreign microelectronics, imported raw materials, Western precision measuring equipment, and overseas-designed software – a reliance that was increasingly pressuring the supply chain.He further added that Russia is currently expending more S-400 air-defence interceptors than it produces and had previously relied on a wide range of imported microelectronics, which it struggled to manufacture locally and can now no longer source. And, though its engineers preferred US-origin high-performance printed circuit board laminates – critical for the S-400’s radar, fire-control, and missile guidance electronics-sanctions and supply constraints had forced them to use alternative sources, potentially compromising system reliability and performance, especially with regard to neutering incoming ballistic missiles.Meanwhile, in a Zoom interview with The Wire last month, Watling said that the S-400s’ manufacturing and support base was under ‘severe strain,’ exposing a proliferating ‘re-supply vulnerability’ reinforced by sanctions, production bottlenecks, and external suppliers that were no longer accessible. Additionally, these strains had also led to open-ended delays in the delivery to India of its two outstanding S-400 systems, he said, complicating its long-term air-defence planning in an increasingly hostile regional environment.Watling said that such collective pressures had created ‘worrisome’ problems for Moscow, forcing it to rely increasingly on Chinese assistance for machine tools used to manufacture precision components, radar and interceptors and other critical sub-systems essential to building and sustaining S-400s and S-500s.And, in areas where Western components were no longer accessible, due to severe export controls and embargoes, he declared that Russia and China had jointly established specialist research units to develop alternative technologies to bridge residual gaps, particularly with regard to semiconductors and microchips.But significantly, he noted that around 70% of the highly complex European, American, and Japanese machine tools Russia acquired in the 2010s to series-build S-400s, were approaching the end of their operational life by 2027. Already constrained by sanctions that limited access to tooling spares, upgrades, and software updates, this aging equipment had created refurbishment delays and reduced production precision. In turn, this had forced Russia to increasingly rely on China for large-scale fabrication and component manufacturing, where recently acquired, comparable tooling had a longer remaining lifespan.“Over time, more and more S-400 components had come under Chinese control, highlighting Russia’s growing technological dependence on Beijing and the proliferating fragility of its domestic manufacturing infrastructure” Watling said.Additional technological and industrial constraints were rooted in the S-400’s production architecture, Watling observed. He said that the operational performance of the S-400 and the newer S-500 air-defence systems depended on two critical components: Active Electronically Scanned Array (AESA) engagement and acquisition radars, and the seeker heads embedded within the interceptors.The radar, produced domestically in Russia, relied on advanced heat-management layers such as beryllium oxide to sustain power output and precision, while the interceptor seeker heads – manufactured exclusively at a facility in Kazakhstan –incorporated high-grade microelectronics and PVC-based laminates, used for insulation and protection of sensitive electronics.However, since many of these critical components were sourced from just a handful of facilities – including the sole Kazakh beryllium oxide ceramics plant – any disruption, whether kinetic, cyber, logistical, or regulatory, could cripple production, refurbishment, and delivery schedules, leaving the S-400/S-500 ecosystem highly susceptible and at risk.Targeted attacks on key Russian installations, like those periodically carried out by Ukraine, could further jeopardise a large proportion of its air-defence ecosystem, potentially degrading its industrial capability. Furthermore, such disruptions would not only delay platform deliveries, but also compel Russia to turn to alternative component suppliers in China, thereby undermining the system’s performance, operational autonomy, and, above all, its sustainment, Watling said.Russia’s deepening reliance on Beijing to sustain the S-400Compounding these technological and industrial drawbacks, internal financial and operational pressures were further straining Russia’s defence sector and thereby the S-400 program, the RUSI analysts said. The widely sanctioned Russian military entities faced higher operating costs, restricted access to credit and profits, and long-term uncertainty over exports and domestic demand, Watling said. Moreover, budgetary constraints and limited financial resources also forced prioritisation of certain programmes over others, intensifying production bottlenecks in IAMDS like the S-400.Hence, in combination – ageing tooling, material and component shortages, and limited financing – demonstrated that Russia’s air-defence systems were heavily constrained by deeper industrial bottlenecks that limited scalability, resilience, and long-term viability, Watling said. These findings, he noted in his RUSI analysis, raised broader questions for countries considering purchasing Russian air-defence systems. While acknowledging that Russia produced some of the world’s most capable IAMDS, he declared that under the prevailing circumstances, it continued to face critical and exploitable dependencies.Amid this stark context, Indian defence planners and industry officials have voiced serious concerns. Responding to RUSI’s assessments, they acknowledged that Russia’s deepening reliance on Beijing to sustain the S-400 created a strategic paradox: in a China-facing contingency – precisely when S-400s or S-500s would matter most – the endurance and sustainability of India’s core air-defence layer could be dictated, or worse constrained, by the logistical and industrial decisions of the very adversary it was meant to deter and potentially confront.‘Such unthinkable reliance on China,’ a senior industry official said in New Delhi on condition of anonymity, ‘would jeopardise India’s wartime endurance and operational autonomy.’ He added that this risk would only grow if the IAF expanded its S-400 inventory, potentially affecting battlefield availability, upgrade cycles, and long-term maintainability. A senior security official, however, put it more bluntly: if this (RUSIs evaluations) were true, the sustainment of India’s S-400 regiments would effectively be dictated by India’s strategic rival, Beijing.Such a putative challenge to Delhi’s defence autonomy sits uneasily atop a bilateral defence relationship with Moscow built over nearly six decades, during which India’s military power has been constructed in substantial measure on Soviet – and later Russian – foundations. From combat and transport aircraft and helicopters to warships, submarines, tanks, missiles, and air-defence systems and a lot else, Soviet and Russian-origin materiel continues to form the backbone of the Indian armed forces, accounting for more than 60 percent of its in-service defence equipment.For long this symbiosis was mutually beneficial: Moscow supplied reliable equipment, generous licensing, and insulation from Western political pressures – especially during the Cold War, when India’s relations with the US were strained. Russia also provided sensitive technologies no Western nations would share, notably those involving the Indian Navy’s ongoing nuclear-powered ballistic missile submarine (SSBN) programme.Yet, long-term sustainment has always been the weak link, and these challenges are not confined to the S-400 alone. While most Indian military officials concede that Russia remained a competent designer of military systems, its capacity to deliver a dependable industrial ecosystem for long-term support is increasingly becoming uncertain – highlighting the vulnerability of a system central to the country’s air-defence posture, as RUSI’s recent S-400 analysis shows.These findings also underscore a stark reality for Indian planners that a weapons system’s durability depended as much on its supply chains as on the hardware itself. In an era of sanctions, logistical warfare, and protracted high-intensity conflict, Indian reliance on Russian materiel is no longer merely a procurement issue–it is a strategic gamble, with mounting risks in which the margin for error was steadily shrinking.