SSNS: THE SILENT VANGUARD OF COERCIVE DIPLOMACY
In modern statecraft, coercive diplomacy straddles the line between diplomacy and war. It is a deliberate application of threats, show of force, or limited military actions to compel an adversary to change behaviour, without escalating into full-scale war. Among the instruments in a nation’s coercive toolkit, the nuclear-powered attack submarine (SSN) stands out as one of the most stealthy, survivable, and flexible assets, for strategic signalling. While inherently offensive, the SSN’s strength lies not merely in its capacity for kinetic warfare but in its psychological and strategic utility as a deterrent and coercive instrument.
This article explores how SSNs, through history and contemporary geopolitics, have evolved into key assets of coercive diplomacy. It examines the theoretical frameworks of diplomacy and coercion, contextualizes SSNs in past confrontations, and argues for their growing salience in the Indo-Pacific and beyond.
DIPLOMACY, COERCION, AND THE SPECTRUM OF CONFLICT
Diplomacy has long been the first recourse of sovereign states in pursuing national interests. In its classical formulation, diplomacy embodies the art of persuasion, negotiation, and communication, conducted through peaceful means. As Hans J. Morgenthau, the father of political realism,
aptly framed it, diplomacy is “the promotion of national interest by peaceful means” and remains a central instrument of power, often seen in contrast to war or coercion. Traditional diplomacy builds trust, crafts alliances, resolves disputes, and, crucially, manages perception — often behind closed doors.
However, in a realist international order, where states are rational actors trying to pursue survival and strategic advantage, diplomacy is frequently infused with power asymmetries and threat calculus. Here emerges a more aggressive offshoot: coercive diplomacy, a method of compelling adversaries to alter their behaviour under the threat of force.
COERCIVE DIPLOMACY: ORIGINS AND STRATEGIC INTENT
The concept of coercive diplomacy gained prominence during the Cold War, when superpowers sought to shape the adversary’s be haviour without trigge ring direct conflict. Alexander George in his work, Forceful Persuasion: Coercive diplomacy as an alternative to war, formalized its theoretical framework, distinguishing it from deterrence. While deterrence seeks to prevent an action, coercive diplomacy seeks to reverse an action already taken.
George emphasized that coercive diplomacy is not about launching a full-scale war, but about demonstrating credible readiness to use limited force, often in incremental and calculated ways to influence the opponent’s decision-making process without losing diplomatic control.
The core components of coercive diplomacy are a clear demand or ultimatum; a threat of punishment for noncompliance; a defined time limit to act or comply; and an offer of de-escalation or assurance if compliance occurs.
A real-world example is the Cuban Missile Crisis (1962), where the US imposed a naval blockade (termed a “quarantine”) to coerce the Soviet Union into withdrawing missiles from Cuba. The US avoided the use of immediate force, but maintained escalation readiness — a textbook case of coercive diplomacy with successful de-escalation (Allison & Zelikov, 1999).
COERCION ACROSS THE SPECTRUM OF CONFLICT
Coercive diplomacy operates within a broader spectrum of conflict, ranging from peaceful negotiation to full military confrontation. It occupies the grey zone — actions that are aggressive, yet fall below the threshold of open warfare. Coercion manifests in several graduated forms:
DEMONSTRATIVE COERCION
This involves visible deployment or manoeuvres such as naval exercises, bomber flyovers, or strategic missile movements to signal capability and intent. These actions are meant to intimidate, not initiate combat. For instance, US naval transits through the Taiwan Strait often serve as demonstrative coercion against Chinese assertiveness.
PUNITIVE COERCION
This includes limited use of force or economic retaliation. Examples range from air strikes on nonstrategic targets, cyberattacks, to, financial sanctions. The US strike on Syria’s Shayrat airbase (2017) after a chemical attack is one such instance signalling resolve without triggering escalation.
FULL COERCION
Here, force is employed overwhelmingly but still stops short of regime change or total war. The 1999 NATO campaign against Serbia, to compel the withdrawal from Kosovo, combined sustained air operations with diplomatic engagement; a blend of diplomacy and punishment.
INSTRUMENTS OF COERCION
Coercive diplomacy uses a range of tools depending on the strategic objective and desired message. Some of the groupings could be as under:
DIPLOMATIC TOOLS: Summons, downgrading of ties or withdrawal of envoys.
ECONOMIC TOOLS: Sanctions, trade embargoes and financial blacklisting.
INFORMATION TOOLS: Strategic leaks, cyber intrusions and influence operations.
MILITARY TOOLS: Troop deployments, blockades, limited strikes, or maritime posturing.
Among military tools, maritime platforms, particularly SSNs (Nuclear Attack Submarines), play an underappreciated but potent role in this matrix. Their ability to convey threat silently, persist undetected, and offer rapid escalation capability without an overt presence makes them ideal instruments for coercive posturing, especially when ambiguity is a strategic objective.
In modern maritime diplomacy, an SSN patrolling off an adversary’s coastline, unacknowledged yet presumed, can influence naval movements, force posture changes, and even delay planned operations. It is the underwater equivalent of a pistol on the negotiating table — quiet, loaded, and always present.
THEORETICAL INTEGRATION: WHERE COERCIVE DIPLOMACY FITS
According to Thomas Schelling, coercion is about manipulating an adversary’s perceptions of pain and gain. It is not merely about capacity but about making the threat of harm credible (Schelling, 1966). SSNs, by virtue of their stealth, speed, endurance, and lethality, introduce a perception of invisible menace, creating uncertainty that tilts the risk calculus of the target state. More ove r, coe rcive diplomacy is tightly linked with the Escalation Dominance Theory, where a state applies pressure just below the adversary’s pain threshold, thereby retaining the initiative while avoiding escalation spiral — a logic central to Cold War strategic doctrines and still relevant in Indo-Pacific confrontations.
TABLE1– SUMMARY OF COERCIVE DIPLOMACY IN THE CONFLICT SPECTRUM
THE ESCALATION MATRIX AND SSNS
The Escalation Conflict Matrix, rooted in Cold War strategy, is a conceptual tool used to understand how conflicts evolve through sequential levels of intensity. One of the most influential frameworks is Herman Kahn’s 44-step escalation ladder, outlined in On Escalation: Metaphors and
Scenarios (1965). Kahn described escalation not as a sudden shift from peace to war, but a graduated continuum where each rung involves greater risk, pressure, and consequences. In modern strategic thought, escalation is often represented not as discrete events but as a continuum of intensifying pressure, typically categorized into four to six progressive bands. It begins with diplomatic actions such as official protests, demarches, or sanctions aimed at expressing disapproval and shaping adversary behaviour. This is followed by non-kinetic signalling, including military exercises, forward deployments, and surveillance operations designed to demonstrate resolve without direct confrontation.
The third band involves, limited kinetic actions like precision air or missile strikes, special operations raids, or cyberattacks intended to coerce or degrade without triggering full-scale war. Next comes full-spectrum conventional warfare, encompassing large-scale land, sea, and air operations with open hostilities. Finally, at the apex lies nuclear or strategic escalation, where the conflict crosses existential thresholds, invoking the most destructive capabilities and strategic decision-making imperatives.
WHERE DO SSNS FIT IN THE ESCALATION LADDER
