The S-400 quandary
- Aviation Features
- The S-400 quandary
15th September 2025
Feature
Mike Mihajlovic considers the claims by both Pakistan and India related to the Indian Air Force’s S-400 ground-based air defence systems
The S-400 Triumf (NATO name SA-21 Growler) formerly the S-300PMU-3, is a mobile long-range surface to air missile system. It’s one of the most capable in the world and feared by most air forces that have to confront it
Images via author, unless stated
India began inducting the S-400 Triumf system in late 2021, marking a significant enhancement of its long-range AD capabilities. Within a year, several regiments were deployed along the western front, with the first unit widely reported to be positioned in Punjab to monitor and secure airspace along the western border. By 2022–2023, additional units were operational, extending coverage to other strategically important sectors. The deployment was a clear signal of India’s intent to strengthen its aerial deterrence posture, particularly against high-performance aircraft and long-range strike assets in neighbouring states.
The JF-17 officially entered service with the Pakistan Air Force in 2010. Initial production runs were completed in China, but as the program matured, manufacturing increasingly shifted to the Pakistan Aeronautical Complex (PAC) at Kamra, enabling domestic upgrades and greater autonomy over the fleet’s configuration. Among the most notable additions to the JF-17’s arsenal was the CM-400AKG, a Chinese-made high-speed air-to-surface missile. Open-source evidence indicates that Pakistan likely acquired the CM-400AKG in the early 2010s, with integration and trials on the JF-17 beginning around 2012–2013. Since then, the CM-400AKG has been a central component of Pakistan’s long-range strike capability. Its inclusion in the JF-17’s armament portfolio expanded the PAF’s ability to threaten heavily defended targets, both maritime and land-based, from standoff distances.
S-400
India’s acquisition of the S-400 system represents a profound enhancement to its AD architecture, one that blends advanced radar capabilities, frequency agility, and networked resilience. At the heart of the system lies a suite of radar sensors: the 91N6E Big Bird for early warning and broad surveillance (over 300-600km), the 92N6E Grave Stone fire-control radar for engagement, the 96L6E Cheese Board low-altitude tracker, and optionally stealth-target detectors such as Nebo-M. These radars collectively create a layered detection envelope, enabling India to detect and begin tracking Pakistani aircraft from long ranges, irrespective of flight altitude or intent to evade.
The S-400 exists in two principal forms: the domestic configuration used by the Russian Aerospace Forces and the export configuration, which is designated by the addition of the suffix ‘E’ to component nomenclature, as in 91N6E for the acquisition radar or 92N6E for the engagement radar. While the export system retains the overall architecture, general capabilities, and versatility of the original design, it incorporates a series of deliberate modifications intended to protect sensitive Russian technology, maintain a strategic advantage over foreign operators, and comply with both national and international arms control regimes.
The four mobile systems that make up the complete S-400 system. From left to right, the 55K6E Command post vehicle, 92N6E target acquisition radar, 91N6E surveillance radar and 5P85SE2/sP85TE2 missile launchers. The 91N6E Big Bang radar is usually parked about 1km from the command and control vehicle, while the 92N6E target acquisition radars can be found between 30-100km away
One of the most significant distinctions lies in radar performance. The domestic 91N6 acquisition radar has been credited, in ideal conditions, with the ability to detect large high-altitude targets at ranges approaching 600km. The export variant, the 91N6E, is slightly reduced in maximum detection range, often cited at approximately 570km, with a marginally lower effectiveness against targets with small radar cross-sections. The reduction in capability arises not only from moderated transmitter power output but also from the deliberate simplification of signal processing algorithms. A similar pattern is seen in the engagement radar. The Russian 92N6 radar can track over a hundred targets simultaneously and engage approximately forty of them at once, employing highly advanced target discrimination routines. The 92N6E generally retains most of this capacity, but in export form, its simultaneous tracking and engagement channels are slightly fewer, and certain adaptive discrimination functions are less sophisticated, limiting its peak efficiency in extremely dense or deceptive air combat environments.
This mock-up of the big CM-400AKG was seen at the Royal International Air Tattoo in July, the weapon’s first public viewing
Chris Lofting
The Russian domestic radars utilise a fully classified suite of counter-jamming features, including high-speed frequency hopping, wideband waveform agility, adaptive beamforming, and dynamic noise rejection algorithms. These allow the system to maintain target tracks even under concentrated hostile electronic attack. In the export versions, these features are retained in a functional but less complex form. Frequency agility remains a prominent characteristic, but the hopping patterns are simplified, and some of the adaptive ECCM (electronic counter-countermeasures) logic is reduced to make the system more predictable for authorised operators while safeguarding Russia’s most advanced techniques from potential reverse engineering.
The CM-400AKG information board displayed next to a mock-up at Zhuhai Airshow in 2019
Alan Warnes
The differences extend beyond the radar subsystems to the missile inventory. The Russian S-400 employs a family of missiles including the 40N6, with a reported range of up to 400km; the 48N6DM, with a range of 250km; and the 9M96E/E2, which are shorter-range but highly agile interceptors. While export clients may receive the 40N6E missile with a nominally similar maximum range, its seeker sensitivity, ECCM robustness, and in some cases actual operational range are thought to be marginally reduced compared to the domestic missile.
A remarkable facet of the S-400’s design is its use of frequency-hopping and beam-steering technologies. These features allow the radar to rapidly switch frequencies in a pseudo-random manner and direct energy precisely toward targets – techniques that severely degrade the effectiveness of enemy jamming attempts. In practice, such agility forces an adversary’s jammer to spread its power across multiple frequencies or attempt to predict the hopping sequence, often unsuccessfully, thus substantially weakening any jamming effort.
India’s deployment of the S-400 goes beyond standalone operation; it is deeply interwoven into the nation’s broader defense sensor network. Systems such as the indigenous Akash AD and Rajendra radar are integrated via the IACCS command-and-control system, helping to correlate radar data from various layers and maintain tracking even amidst jamming or signal interference. The Rajendra, a passive phased-array radar, can track multiple targets and issue missile guidance commands, even under intense electronic warfare conditions.
A JF-17C Block 3 Thunder launched the CM-400AKG missile at the IAF’s deadly S-400 air defence system. Two members of 14 Squadron ‘Tail Choppers’ were awarded the third highest military honour, Sitara-i-Jurat (Star of Courage) for their part in the mission
Alan Warnes
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