RUSI Flags Russia’s S-400 Vulnerabilities, Raises Questions for India

A December 2025 report by the Royal United Services Institute (RUSI) has detailed significant Russia S-400 vulnerabilities, showing that Moscow’s flagship air defence systems remain heavily dependent on imported components despite years of sanctions.

The findings carry implications for India, one of the largest foreign operators of the S-400 system, particularly regarding long-term sustainment, upgrades, and spare parts availability.

Foreign Components Critical to Russian Air Defence Production

According to the RUSI report, Russia “continues” to rely on foreign-sourced materials for radar, guidance, and testing subsystems used in the S-400 and the newer S-500.

Trade data cited in the report shows that U.S.-manufactured high-frequency laminates produced by Rogers Corporation were imported into Russia in 2024 through third countries. These materials are used in radar printed circuit boards essential for phased-array radar performance.

In parallel, Russia imported beryllium oxide ceramics from Kazakhstan, valued at nearly USD 18 million in 2024. These ceramics are critical for thermal management in high-power radar systems and have not yet been sanctioned.

Production Sites Exposed to Disruption

The report maps over fifty Russian defence manufacturing facilities linked to air defence production. Key sites include NPO Almaz in Moscow and JSC Radiozavod in Penza, which handle guidance and control systems.

Several of these facilities lie within 350–500 kilometres of Ukraine, placing them within potential reach of emerging Ukrainian long-range strike capabilities. Short-range air defence production is also concentrated in Tula, creating geographic concentration risks.

Sanctions Evasion Sustains Output

RUSI notes that Russian production has not collapsed due to layered fallback arrangements. These include routing controlled components through Kazakhstan, Turkey, China, and the UAE.

Chinese substitutes increasingly replace Western components. However, the report states that these alternatives degrade performance, raise rejection rates during testing, and increase production costs.

Domestic substitution efforts remain limited. Russian industry still depends on Western design software and calibration equipment, much of it obtained through indirect channels.

Ageing System Architecture Compounds the Problem

The report places the vulnerabilities in historical context. The S-300 family dates back to the late 1970s, while the S-400 entered service in 2007 but is rooted in 1990s technology.

The newer S-500 programme has faced repeated production delays, partly due to shortages of specialised materials and electronics. Shared components across these systems amplify supply chain risks.

Implications for India’s Russian S-400 Fleet

For India, the report does not suggest immediate operational degradation of deployed S-400 systems. However, it highlights long-term risks related to spares, replenishment missiles, and radar component replacements.

In a constrained sanctions environment, Russia may prioritise domestic military requirements over export customers. This could affect delivery timelines and component quality for foreign operators.

Strategic Exposure and Technology Transparency

The report also notes that extensive battlefield analysis of Russian air defence systems in Ukraine has increased Western technical understanding of these platforms.

While India operates Russian S-400 AD independently, shared design lineage means system limitations are now better understood by NATO militaries, raising questions about survivability in high-end conflict environments.

Why the RUSI Report Matters

RUSI emphasises that the findings are not new discoveries for Western intelligence agencies. Instead, the report consolidates open-source trade data, captured equipment analysis, and Ukrainian operational insights into a public assessment.

For India, the report reinforces the importance of diversified air defence layers and domestic manufacturing capacity, rather than dependence on any single foreign supplier.

Indian Strategic Takeaway

India’s Russian S-400 induction remains a key pillar of its air defence architecture. However, the RUSI report highlights that sanctions, supply chains, and geopolitics directly affect long-term system sustainment.

As India advances indigenous air defence and missile defence programmes, the findings reinforce that operational sovereignty depends as much on industrial resilience as on acquisition decisions.

At the same time, defence analysts caution against treating the RUSI findings as a strategic revelation. A counter-view emerging in policy circles holds that the report largely amplifies issues U.S. intelligence agencies have tracked for years rather than exposing new weaknesses. Washington has long monitored Russia’s dependence on foreign components and has repeatedly tightened export controls, intelligence-sharing mechanisms, and secondary sanctions.

However, enforcement has remained a cat-and-mouse exercise. Moscow has adapted through rerouting, substitution, and fallback arrangements. Russia, aware since at least 2014 that the West understands these vulnerabilities, has spent over a decade building workarounds to sustain production under sanctions. From this perspective, the RUSI report reflects continuity rather than shock, highlighting the limits of economic warfare rather than a sudden collapse in Russian air defence capability.