SOURCE: AFI
The combat debut of India’s S-400 Triumf air defense system during the India-Pakistan clashes in May 2025 has sent ripples through regional defense circles, particularly in China. Analysts from the Chinese internet service Sohu have expressed surprise at the system’s effectiveness against Pakistani forces, noting that it outperformed expectations based on China’s experience with its own S-400 units.
According to Sohu, the S-400 systems delivered to China appear to be a significantly simplified export variant, with key advanced functions deliberately blocked by Russia to protect its technological secrets. This revelation has sparked debate about the strategic implications of export restrictions and their impact on China’s defense capabilities, especially as Pakistan’s Chinese-supplied systems faced challenges against India’s S-400.
India’s S-400 Triumf, known locally as Sudarshan Chakra, made its combat debut on May 7, 2025, during Operation Sindoor, a series of Indian airstrikes targeting terrorist camps in Pakistan and Pakistan-occupied Kashmir (PoK). Indian media and defense officials credited the S-400 with intercepting Pakistani drone swarms and missiles, with a notable claim of downing a Pakistan Air Force (PAF) Saab 2000 Erieye airborne early warning and control (AEW&C) aircraft at an unprecedented range of 314 km. This performance underscored the S-400’s advanced capabilities, including its 600 km detection range and ability to engage targets up to 400 km away using missiles like the 40N6.
The system’s success contrasted sharply with Pakistan’s Chinese-supplied HQ-9P air defense system, which has a range of 120–300 km depending onshadowed Indian Rafale fighters, armed with Meteor missiles, and indigenous systems like the Akash, India maintains a multi-layered air defense network that outclasses Pakistan’s capabilities, further highlighting the S-400’s strategic edge.
Chinese analysts from Sohu, a prominent online platform, expressed surprise at the S-400’s performance in India’s hands, noting that it appeared far more effective than the systems China received from Russia under a $3 billion deal signed in 2014. According to their analysis, Russia supplied China with a downgraded export variant of the S-400, referred to as the S-400K, which lacks some of the advanced functionalities present in the Russian and Indian versions. “Apparently, export versions of the S-400 may be limited in key technologies,” the Sohu report stated, suggesting that Russia deliberately restricted access to critical features to safeguard its technological secrets and prevent foreign militaries, including China’s, from matching Russian air defense capabilities.
Sohu analysts revealed that Chinese specialists attempted to reverse-engineer and access the blocked functions of the S-400 to integrate its technologies into indigenous systems like the HQ-9 series. However, these efforts were largely unsuccessful. “The (Chinese) military’s efforts to gain access to the blocked functions of the S-400 were also unsuccessful. As a result, all these attempts were abandoned, and the systems were deployed in the south of the country,” a Russian news portal cited by Sohu reported. This admission highlights China’s frustration with the limitations imposed by Russia, which reportedly include a “kill switch” and other safeguards to prevent unauthorized access to sensitive technologies.
A Russian defense source, when asked for comment, confirmed the practice of incorporating in-built safeguards in export models to protect Russian assets in potential conflicts with buyer countries. This strategy not only prevents technology transfer but also ensures that Russian forces maintain a qualitative edge over foreign operators of the S-400, such as China and Turkey.
The revelation of a downgraded S-400 variant has raised concerns in Beijing about the system’s effectiveness in its arsenal, particularly in the context of regional tensions with India. China, which operates its own S-400 units along the Line of Actual Control (LAC), had hoped to leverage Russian technology to enhance its HQ-9 and FD-2000 systems, which are based on older S-300 technology. The HQ-9P, deployed by Pakistan, proved less effective against India’s S-400, with a shorter range and less sophisticated radar, underscoring the technological gap.
Posts on X have speculated that Russia shared source code and modification permissions with India, enabling greater operational flexibility, while China received a restricted version. This disparity has fueled perceptions that Russia prioritizes India as a strategic partner, especially amid declining Russian arms exports, which fell 47% since 2022 due to reduced orders from both India and China. China’s inability to fully replicate S-400 technologies has prompted a reassessment of its air defense strategy, particularly as India’s multi-layered defenses, combining S-400, Akash, and Israeli Barak-8 systems, continue to outpace Pakistan’s capabilities.
The S-400’s performance also has broader implications for South Asia’s arms race. Pakistan’s use of Chinese-supplied PL-15E air-to-air missiles and CM-400AKG hypersonic missiles, launched from JF-17 Block III fighters, marked their combat debut in May 2025. However, claims by Pakistan and Chinese state media, such as Xinhua, that the CM-400AKG destroyed an Indian S-400 unit in Adampur, Punjab, were debunked when Prime Minister Narendra Modi posed in front of an intact S-400 system during a visit to Adampur Air Base on May 13, 2025. This incident highlighted the limitations of Pakistan’s air defense and strike capabilities, further amplifying China’s concerns about its own S-400 systems’ restricted functionalities.
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