Ballistic Missile Defence: A Bulwark of Deterrence

by Vice Admiral (retd) Vijay Shankar

This article is forthcoming in the March 2019 issue of Geopolitics

In the aftermath of the Six-Day war of 1967, there ensued a prolonged period of sporadic hostilities between Israel on the one hand and Egypt, Syria and Iraq on the other. On 12 October, 1967, the Eilat, an Israeli Destroyer on routine patrol, was engaged in a surface action by Egyptian missile boats off Port Said. A crew member on the deck of the Eilat apparently did not understand what he was looking at. It was not a rocket; it was a Styx missile, the first of four that slammed into and sank the hapless destroyer. Of the incident, the Captain of the Eilat recorded “I stood there transfixed, watching the missile”. The 1971 Indian missile strikes on Karachi port installations and warships defending the harbour evoked a similar distressed response. It was another reminder of the need for effective defence against missile attacks.

And just as the ‘Defence’ came to grips with the nature of missile assaults through a combination of deception, soft and hard kill measures, the ‘Offence’ wrested the initiative through enhanced ranges, precision, speed, cruise altitude, deception, unpredictable targeting and more significantly by adopting a sub-orbital ballistic trajectory with a multiple independently targetable re-entry vehicle payload containing several warheads, each capable of being aimed to hit a different target.

Approach to Ballistic Missile Defence: Effectiveness

While the debate on whether or not India should test and deploy ballistic missile defences (BMD) is now largely settled, the important question of how effective such systems are likely to be remains ‘iffy’. The answer to this question depends on considerations such as type of defence, characteristics of the attacking missile, desired kill probability, standards for measure of success and lastly the economics of induction which will determine how secure and gapless coverage can be achieved.

Indian backers of BMD argue that trials have already proven the system to be effective. Critics, however, maintain that these trials are too few, unrealistic and structured-for- success; contention being that they do not in any way attempt to mimic the ‘fog’ and unpredictability that generally envelopes operational situations which will eventually have a bearing on measure of effectiveness. The quandary is that there is not enough empirical data to arrive at an objective assessment.

Given the contrapositions in the debate, it is necessary first to understand the features of a ballistic trajectory in order to discern opportunities available to the Defence.

The Ballistic Trajectory and State of Play

Assuming the missile’s range is long enough that it leaves the atmosphere; a ballistic missile’s trajectory is typically divided into three phases.  First, the boost phase, when the missile is under powered flight using its rocket booster.  Second, the midcourse glide, in which the missile coasts on a ballistic trajectory through outer space.  Third, the terminal phase, in which the missile or warheads re-enters the atmosphere and plunge towards its target at hypersonic speeds.  Each phase presents different options and problems for the Defence.

Hard-kill systems (measures that physically counterattack an incoming missile destroying/altering path of  its warhead) that operate within the atmosphere or above it such as the U.S. Army’s Patriot system, the U.S. Navy’s Aegis system, the Russian S-400 system and indeed the Indian BMD, a double-tiered system consisting of two land and sea-based interceptor missiles, namely the Prithvi Defence Vehicle (PDV) missile for high altitude interception, and the Advanced Air Defence (AAD) missile for lower altitude interception. All these systems use radar for guidance and homing and most are equipped with high-explosive warheads while some use kinetic impact for destruction of the incoming missile. Aero-dynamic forces enable interceptor manoeuvring and “atmospheric filtering” resolve ambiguity posed by countermeasures.  In the 1991 Gulf War, the Patriot or PAC-2 interceptor missiles, reportedly, attempted to intercept 44 Iraqi Scud ballistic missiles. The U.S. Army by their own estimates (which varies wildly), claimed kill percentage of about 61%. However, technical analyses suggest that the actual intercept rate was nearer to zero. In the 2003 Iraq War, the U.S. Army fielded the improved PAC3 BMD, evidence is mixed on whether the system actually performed since there had reportedly, been only two “kills” in seven launches.

Boost-Phase Interception

Boost-phase interception attempts to destroy missiles while they are still in powered flight.  This mode of defence, in concept, could use hard-kill interceptors, or beam weapons such as lasers.  Boost-phase defences have some significant advantages over midcourse or terminal interception. Importantly, destroying a missile during boost eliminates all of its warheads and therefore is most appropriate against missiles equipped with multiple warheads. In addition, the problem of countermeasures appears to be much less severe for boost-phase interceptors than it is in midcourse or terminal phase engagements. The difficulty facing boost-phase defence is, time for engagement that the hostile missile offers which at most is a few minutes; suggesting that a boost-phase interceptor be located relatively close to the attacking missile launch site. This consideration become critical when it comes to neutralising short ambit ballistic missiles which by virtue of limited range may have to be deployed in the tactical battle area such as Pakistan’s Nasr or their Hatf 1 and Hatf 2, missiles. The launch vehicle could be eliminated prior to missile launch by precision guided munitions or air to surface missiles.

Midcourse Interceptors

Long-range midcourse defence operates above the atmosphere (exo-atmospheric) and refers to that part of the target’s trajectory after its booster rocket has burned out but before it begins to re-enter the atmosphere. It aims at direct collision homing techniques during target travel through space.    Midcourse interception in principle provides wide area defence. At the same time exo-atmospheric mode of operation makes the Defence potentially vulnerable to a variety of countermeasures. A primary objective of such defences is countering nuclear-armed missiles. Very few nations have proven the efficacy of midcourse interceptors, for the real issue is not its theoretical viability or how well it works on a test range, but its operational effectiveness – that is, how well they can be expected to work given unpredictable circumstances in an environment where countermeasures are deployed. Unfortunately, very little open source information is available on the matter.

The Russian S-400 system would appear to have captured the wide area midcourse BMD market for reasons of effectiveness and economy. Its closest rival is the American Patriot PAC3; both systems claim a dual capability of shooting down aircraft and providing BMD. It would now help our analysis if consideration is given to the known attributes of the two systems. A comparison of technical parameters indicate that the S-400 can shoot down targets moving at a speed of 17 km/sec while the PAC-3 limit of target speed is 8 km/sec; in terms of simultaneous tracking and engagement the S-400 can track 160 targets and engage  72 targets simultaneously while the PAC3 can track125 and engage 36. Maximum tracking range for the S-400 is 600 km and kill range is 400 km while the PAC3 tracking and engagement range is far less at 180kms and 100kms respectively. The S-400’ altitude aperture is from a low of 10 metres to a high of 30 km while the Patriot’s altitude bracket is between 50 metres and 25 km. To achieve a kill probability of not less than 0.99, the S-400 will have to launch a salvo of 2 missiles while the Patriot, 3 missiles. It would now be apparent that in all vital attributes the S-400 outperforms the PAC3. Also, it is interesting to note that the Russian system has the capability to detect stealth aircrafts such as the US F-35 and Chinese J-20 which are characterized by a low radar signature. Five squadrons of the S-400 system are expected to be inducted into India’s inventory by 2020 at a cost of $ 5.43 billion.

India’s Rough Nuclearized Neighbourhood

A nuclear deterrent relationship is founded entirely on rationality. On the part of the ‘deteree’ there is rationality in the conviction of disproportionate risks of hostile action; and on the part of the deterrer rationality of purpose and transparency in confirming the reality of the risks involved in a manner that strategic miscalculations are avoided . The exceptional feature of this transaction is that the roles are reversible provided it is in the common interest to maintain stability in relationship. The rub when dealing with Pakistan is that political leadership is a charade that masks the real manipulators of power: the military establishment, who, as a rule do not expose themselves to diplomatic parleys and the tedium of negotiations.

India’s neighbourhood in nuclear security terms is significant for the two nuclear armed neighbours that quarter its Northern and Western borders. Both inimical to its interests; the former Machiavellian in its security relationship while the latter out-and-out pernicious and perhaps more alarmingly a nuclear surrogate whose arsenal and doctrine have been devised, tested and phrased in Beijing.

In all but two doctrinal precepts there does not appear to be great divergence between China’s and India’s Nuclear Doctrine. Where China deviates is on the subject of ‘the demonstration’ and ‘doctrinal dynamism.’ The former suggests, in the abstract, that nuclear weapons would be used, if credibility is ever questioned. This usage may not be against vital targets and yet will leave no doubts of intentions. While the latter opens up the nature of their alliances. In this frame of reference, the scripting of the Pakistan nuclear capability, transfer of nuclear technologies, developing their strategic and tactical nuclear arsenal, setting up of the Khushab I to IV weapon grade plutonium production reactors and the emergence of a first-strike capability becomes significant.

Thus, China’s doctrinal dynamism potentially permits a Janus-faced policy – the one that it presents to the world at large is that of the No-First-Use (NFU), minimalistic, rigid, restrained nuclear power while the other is to retain the First Use alternative through the Pakistan arsenal. This policy has placed nuclear force planners in a quandary; not to respond is to open India to a possible degradation of their Second Strike capability. China moulding Pakistan’s nuclear First Use facility, forgets the fact of an enfeebled Pakistan civilian leadership incapable of action to remove the military finger from the nuclear trigger; the active involvement of UN designated terrorists in military strategy and an alarming posture of an intention-to-use; all have the makings of a global nuclear nightmare.

Given the opacity of Pakistan’s strategic nuclear underpinnings, descent to tactical nuclear weapons (TNW) and duplicity of policies, it has become increasingly prickly for India to either understand nuclear thinking in Islamabad or to find coherence between a mania for parity, the rush for stockpiling fissile material and the loosening of controls over nuclear weapons. More puzzling is the notion that the conventional imbalance between the two countries may be countered by Pakistan introducing TNWs as “another layer of deterrence” (ala NATO’s discredited formulation). Clearly in this strategic framework, the generation of India’s BMD cannot come as a surprise to any pundit of nuclear security.

The Indian BMD

India is in the advanced stage of developing and deploying a multi-tiered BMD system designed to achieve exo-atmospheric interception of short, intermediate, and intercontinental range ballistic missiles during midcourse flight interfaced with an endo-atmospheric hit-to-kill interceptor. The system consists of a two stage, solid propellant Prithvi Defence Vehicle (PDV) missile in tandem with the Advanced Air Defence (AAD) Missile for high and low altitude interception, respectively. The PDV intercepts ballistic missiles at exo-atmospheric altitudes up to 150kms while the AAD missile achieves endo-atmospheric engagement within an altitude envelope of 15mtrs-30kms. The AAD is also effective against cruise missiles and short range ballistic missiles. The system is interfaced to a long range phased array tracking radar (Swordfish) which provides gapless surveillance up to 1500kms. The deployed system would consist of several launch vehicles, radars, Launch Control Centres grouped under a Mission Control Centre. All these are geographically distributed and connected by a secure communication network

The Russian S-400 Triumf BMD system to be inducted by India beginning 2020 (operational parameters discussed in some detail earlier) when married and deployed with existing endo-atmospheric systems such as the AAD or Barak 8 (joint Indo-Israeli production), will provide significant strategic performance upgrade to India’s BMD capability. Particularly in the face of China’s intermediate and intercontinental ballistic missiles of the JL2 and DF31A type; Pakistan’s nuclear arsenal of medium range ballistic missiles such as the ‘Ababeel’, cruise missiles such as the ‘Babur’ and tactical ballistic missiles of the ‘Nasr’ type. While capability to neutralise the ballistic missile threat from both India’s nuclear neighbours is credible, what may be questioned is the economics of the matter and how selective or otherwise can India be in providing BMD cover to counter force and counter value targets.

Impact on Deterrence

The point at issue that planners will raise is: in what manner does the Indian BMD serve the cause of deterrence? Cold-war theology that drove the bi-polar deterrent relationship between USA and the USSR hinged on an axiomatic logic of Mutually Assured Destruction (MAD) and the strategic rationality (that both protagonists subscribed to) which provoked ‘predictable behaviour.’ Thus, in that era, the BMD became a de-stabilizing factor as it undermined the shared hostage situation that was central to MAD. Also, it set into motion dynamics for modernising and enlarging nuclear arsenals. It is in this sensibility that the Anti-Ballistic Missile treaty of 1972 was considered ‘the bedrock of strategic nuclear stability.’

Answers may be found in the changing shape of geopolitics at the turn of the 21st century that not only fractured the former bi-polar equilibrium to multi-polar uncertainties, but also introduced reprobate nuclear armed states into the milieu, some of whom are not so readily convinced of the logic of MAD or the strategic rationality of ‘predictable behaviour.’ Pakistan finds itself in this category. The deterrence of such states poses a dilemma never faced before, for reasons of their often repeated capricious nuclear threats and intent-to-use policy, decentralized control of TNWs and their military strategy that finds unity with terrorists; all of which places pressures on states with stable and reposeful nuclear doctrines such as India. Consequently, for India, deterrence is not just a function of strategic rationality but, of persistent emphasis on credibility of the power to deny and the immense and exacting shock of response. It is to further this precept that the Indian BMD finds expression.



The Dilemma of a Threshold

In nuclear policy parlance, ‘threshold’ indicates when and under what conditions leadership may resort to the use of nuclear weapons


Vice Admiral (retd.) Vijay Shankar

(Published in the author’s column “The Strategist” on the IPCS website and available at

The nuclear planner is acutely involved in analysis of when and under what political conditions opposing leadership (military or otherwise) may resort to the employment of nuclear weapons. For nations with a policy of No-First-Use (NFU), the answer is “in response to the first-use (FU) of a nuclear weapon under conditions as stipulated in the doctrine.” However between nuclear armed nations, the one with a FU policy is faced with a more complex set of issues which will invariably raise the question “are political ends served with first-use of nuclear weapons knowing that an escalatory response may well be massive and place value targets in its cross hair.” Does first-strike come paired with the ability to offset a nuclear response? Indeed there is the theoretical possibility that the first strike may altogether neutralise the opposition’s capability of nuclear response; but this, as the evolution of nuclear thought and development of nuclear arsenals have shown, is a fantasy. Even the smallest retaliation in a nuclear exchange targeting a city will imply horrific destruction that the first striker must contend with. To put matters in perspective consider the following: the destructive potential of a nuclear weapon say a 20 kiloton nuclear weapon airburst targeting a city such as Karachi (in 2017 Karachi’s metropolitan area population was estimated at 23 million) with a population density of 24,000 per square kilometre will result in at least 8,00,000 primary casualties and another 12,00,000 secondary (statistics approximate based on casualty curves, Abraham Henry, Nuclear Weapons and War, 1984).  Or, one only has to recall the geographic extent and casualties of the 1986 “Chernobyl” power plant disaster to appreciate that the hazards of a nuclear encounter are not abstract notions. The radiation fallout spread from Scandinavia to the Black sea, over 116,000 people were affected while Belarus has since shown a 2400% annual increase in the incidents of thyroid cancer.

The capability to respond unfailingly and credibly lies at the heart of a deterrent strategy driven by a NFU policy. Faced with the certainty of appalling destruction in response to a nuclear adventure, why an aggressor should contemplate a first-use of nuclear weapons remains bizarre since it is at odds with the very idea of survival. Whatever may be the conditions of the conflict; the approach of such a threshold when one or the other protagonist may reach for the nuclear trigger must not only be transparent but be declared so that a return to normalcy becomes viable.

The strategic irony of dealing with Pakistan is that not only is it armed with nuclear weapons, but also forewarns ‘first-use’ shorn of a declared doctrine. The weapon, as recent statements from their establishment suggest, is “India specific” and the development of their nuclear arsenal is to deter India’s conventional forces from offensive operations through the use of tactical nuclear weapons (!) and should that elicit a massive response then that would be countered by an assured “limited” (?) second strike capability (a conversation with Khalid Kidwai, 2015). The latter, in their view, serves to “stabilise” the former; never you mind what or who caused the primary provocation. The doctrine remains under a cloak of ambiguity emboldened by the belief in a, yet to be developed, sea-based second strike launched from conventional submarines.

The first deduction that may be made from such a policy is that Pakistan has adopted a nuclear war-fighting doctrine notwithstanding a dangerous absence of technology necessary to provide intelligence, surveillance, reconnaissance (ISR) and command and control on land, at sea and in the air. The second deduction is, between their first and second strike Pakistan is convinced of surviving massive retaliation with its second strike intact. Is this a reasonable assumption or is it more bravado than sense? The third understanding is, when such a nuclear doctrine remains cloaked in ambiguity the separation between the Nuclear and principles that govern conventional warfare are blurred. This attains a catastrophic bent significantly when conventional principles such as surprise and deception are integrated into a first or a second strike plan, for the unsaid implication is that Pakistan, in some woolly manner, holds sway over the escalatory dynamic.

In all this what alarms is the lowering of the nuclear threshold while exposing the weapon to unintended use in its movement into the tactical battle area and the truancy of centralised command and control. Also, the deterrent value of the weapon from the standpoint of both time and space is narrowed if not foreclosed. Two more issues need to be recognised relating to the vexed geography of the Indo-Pak situation; the Line of Control (LoC) demarcates extent of geographic control over disputed territory in Jammu and Kashmir, to advocate creating a nuclear wasteland in territorial hankerings does not quite make strategic sense. It is equally clear that, among nations that share common borders, a nuclear exchange will spread devastation irrespective of man-made boundaries.

In the early stages of Pakistan weaponizing its nuclear capability it had, indeed, gestured to where its nuclear threshold lay. As could be deciphered, first-use of nuclear weapons was predicated on four thresholds:  large territorial setbacks, comprehensive military attrition, economic collapse and political precariousness. The deterrent logic these thresholds described was really quite unmistakeable for they also provided to Pakistan a context for maintaining conventional power. However, this rationality flew in the face of the acquisition of tactical nuclear weapons (TNWs). The perception widely held among commentators in India is that the four threshold doctrine has since been trashed. “Full-spectrum deterrence” is what Pakistan today makes its arsenal out to be. Central to this doctrine is the integration of TNWs with conventional forces and a callow belief that the nuclear escalatory ladder is in control of the first striker. This abstruse doctrinal tangle suggests that Pakistan not only fails to take account of India’s nuclear response but is also convinced of their ability to initiate a nuclear war and survive unscathed from the encounter.

To establish where Pakistan’s nuclear threshold lies conceptually is a baffling task. However, for Pakistan to escalate to the nuclear dimension in response to an Indian conventional riposte to a major terror assault traced to GHQ Rawalpindi cannot be consistent with their “full spectrum” doctrine since the riposte does not come as a result of the latters failed conventional action which is the “first tier” of the spectrum. Rather, in this frame of reference, the nuclear first-use threshold must be assessed in the context of political realities, state policy that finds unity with jihadists and military capability. An ambiguous nuclear doctrine in these circumstances cannot alone determine the nuclear threshold; what it can do is calibrate the uncertainty that it imposes and in the process limit both extent and intensity of the riposte.

Nuclear thresholds are neither fixed by geography nor by time but determined more by severity and purpose of military action, which by some national gauge or a combination of triggers, will lead to the decision that a threshold has been breached. As may be deduced from Pakistan’s peace-time nuclear posture, lack of high-technology-persistent-ISR, absence of a cyber and outer-space capability, and the fragility of the second strike, their nuclear threshold may not lie at the low end of the scale. Reason being the first tier of the spectrum may not have quite ruptured in the early stage of a crisis while the second strike remains unfledged. And yet it is equally clear that threat of nuclear use has been brought out of the backdrop to a position from where nuclear deterrence becomes a looming immediacy.