The S-400 deal with Russia, comes as a mixed bag with gains at best being political. On balance it would be safe to say that militarily, despite the S-400's formidable capabilities (as advertised) will not translate into a serious game changer on the ground, and its purchase costs may be misleading as its integration may turn it into a white elephant that could bleed the military down the line.
What we need to be clear about is that on paper, the S-400 is a formidable capability against aircraft. It has very long range and ability for extreme manoeuvres, which means that most aircraft it will face up against, will theoretically be mincemeat. Sadly, the reality may be different. It is safe to say that Pakistan's late purchase F-16s may have significant jamming capabilities against the S-400 as the life cycle of these late production F-16s and access during production to the US's updated threat database would have accounted for the S-400 threat.
Moreover being a radar-guided missile, it is fairly safe to say that China's new generation of stealth fighters will be able to evade it. Knowing this, the Russians have, however, based their entire strategy on the S-400's potency when used on a system of systems. This involves heavily networked radars operating at different wavelengths that, for the Russians, create a multiple-verified and hence accurate targeting solution, but for the enemy creates a confusing cacophony of signals that are impossible to jam simultaneously. Yet it seems that India is buying the system as a standalone. Despite claims that it will be networked into an Indian system of systems, the political reality is the Russians will never allow their prized system to be interoperable with systems that are viewed as adversarial and are manufactured by US, European and Israeli companies. India's hopeless air defence network is already a white elephant of US, Israeli and European systems, which talk to each other but do not, or are not allowed to, talk to non-NATO systems. Moreover, they have also been degraded precisely because of the danger of their technology being compromised, if linked up to Russian systems.
Even in the anti-aircraft role, given the political climate of hostility between the West and Russia (including France cancelling the sale of downgraded helicopter carriers to Russia) means that not one western aircraft system available to us, be it the Rafale or the winner of the 100 aircraft MMRCA competition, will get political clearance for deep integration with the S-400. What this means is that our aircraft will run the risk of being shot down by our own S-400s. Supposing the rudimentary integration of modern western combat aircraft (which is a technological possibility, despite political opposition from the supplier country) with the S-400 takes place, it will reduce both the combat aircraft's ability to carry out unfettered operations, as well as severely restrict the S-400's ability to carry out unfettered anti-aircraft operations for fear of shooting down one of our own prized assets. Any statements to the contrary must be deemed as delusional unawareness of political, economic or technological reality, as what is being asked of both the Russians and the West is to compromise their technological secrets to someone they see as adversarial. Moreover allowing such integration also reduces the attractiveness of the system being exported to other countries, as both the West and Russia have their own captive markets that face off against each other (for example a western-supplied Saudi Arabia against a largely Russian-supplied Iran, a western-supplied Israel against a Russian-supplied Syria and Iran, and a western-supplied Japan and South Korean facing off against a mostly self-sufficient China that frequently relies on Russian military imports).
Worryingly, Russian sources are also clear in private conversations, that while the S-400 is a formidable system against aircraft, it is subpar in its ability to intercept ballistic missiles, mostly because of the known weakness of Russian systems in terminal phase accuracy, due to poor electronics and an industry still stuck in the 1980s technology groove. Ultimately, no amount of extreme manoeuvring can overcome a lack of accurate targeting. In the case of aircraft, the S-400 overcomes this be having a massive warhead with a large blast radius that can tear an aircraft to shreds despite detonating at a distance. With intercepting missiles, given that the intercept window can be vast, a lack of accuracy is fatal. Moreover Ballistic Missile Defence (BMD), unlike other military solutions that you can opt for, leans heavily on quantity or quality as binaries. An effective BMD requires great quantity, in great and brutally unforgiving quality. That is to say, it is not just enough to have a few very accurate missiles or have many less accurate missiles. You need plenty of highly accurate missiles with the associated costs.
Effectively then, the military case for the purchase of a limited number of S-400 systems is bogus and this then brings us to the political argument. This argument goes that since the Russia-India bilateral relationship has, since the 1990s, become a weak one narrowed down to energy and military cooperation, there is a need to throw defence contracts at the Russians whether the military need exists or not. This argument becomes even more acute considering the precipitously declining standards of Russian military industries and the Indian military's increasing reluctance to buy from Russia (given the abandonment of the joint 5th generation fighter programme). This is a valid point. However, one should also consider the political opportunity cost, in that though India now has access to advanced western equipment by default, the induction of advanced Russian systems means that every purchase of an advanced western system becomes a political negotiation point with the supplier either imposing restrictions or downgrading the equipment that will be sold to us. Equally, it may also preclude the sale of advanced systems such as stealth drones or the F-35, unless concrete guarantees are given that the S-400 will not be linked up and operate as a standalone.
Even excluding the superficial western commentary on how this will be a game changer that presages a counterforce posture and forces Pakistan to ramp up its nuclear and military posture (and make no mistake, Pakistan will, even if it perceives the S-400 to be a limited threat), it is safe to conclude that India's purchase of the S-400 is at best an ad-hoc move with illusory tactical advantages, significant political costs and quite possibly a strategic setback.
Abhijit Iyer-Mitra is Senior Fellow at the Institute of Peace and Conflict Studies (Twitter: @Iyervval)