Shabnam Shabani

October 2025

“No nation can make its survival dependent on the goodwill of another state… especially a state that announces a hostile ideology”

–Henry Kissinger, Former United States Secretary of State

Since its emergence as a distinct school of thought, realism has centred upon the assumption that international politics is defined by anarchy, competition, and the struggle for power. Within this tradition, defensive realism contends that states can achieve security not by maximising power indefinitely, but by maintaining sufficient capabilities to deter aggression and preserve survival. The question arises, however, as to whether such a defensive approach is capable of guaranteeing security in practice. The case of Israel offers a particularly revealing test.

Since its establishment in 1948, Israel has confronted a uniquely hostile environment, with security threats emanating not only from neighbouring states but also from non-state actors backed by regional rivals. In recent decades, Iran has emerged as the foremost adversary, projecting influence through the “Axis of Resistance” and directly challenging Israel’s deterrence posture. From the 7 October 2023 attacks, to the unprecedented Iranian missile and drone strike on Israel in April 2024, and culminating in the open Israel–Iran war of mid-2025, Israel has faced sustained assaults despite its robust defensive measures and status as a de facto nuclear-armed state.

This essay argues that Israel’s realist security strategy has been partially successful: it has secured regime survival, deterred conventional invasions, and maintained a qualitative military edge with vital external support, particularly from the United States. Yet defensive realism has not guaranteed security. Instead, the persistent escalation with Iran and its network of proxies demonstrates that defence alone cannot resolve the security dilemma; rather, Israel’s policies have often spilled into offensive realism, fuelling further instability. By evaluating Israel’s experience against criteria of state survival, deterrence credibility, escalation control, and societal costs, this study will demonstrate both the strengths and the limits of defensive realism in contemporary international politics.

Realist Toolkit

Realism rests on the assumption that international politics operates under anarchy—an absence of a central authority capable of enforcing order among states. In such a system, power and security are the fundamental currencies, and survival is the primary goal. Classical realists stressed the human propensity for power-seeking, while neorealists attributed it to structural constraints. This structural account underpins two strands of realism most relevant to Israel’s experience: defensive and offensive realism.

Defensive realism, associated with Kenneth Waltz and refined by Charles Glaser, argues that the international system encourages states to seek an “appropriate” level of power. Since security can be maintained through deterrence and balance-of-power mechanisms, expansion is unnecessary and often counterproductive, as it provokes counterbalancing and increases insecurity. Defensive realism thus centres on restraint, deterrence, and survival through maintaining a sufficient but not excessive military posture.

Offensive realism, articulated by John Mearsheimer, holds that the international system compels states to maximise relative power whenever possible. As states can never be certain of others’ intentions, security cannot be guaranteed through moderation. Consequently, great and regional powers pursue expansion, pre-emption, and hegemony where feasible. For offensive realists, restraint is perilous; only the accumulation of power ensures survival.

The relationship between these strategies is explained by the “security dilemma.” Robert Jervis notes that when states increase their security—by building defences or acquiring weapons—others perceive it as threatening, triggering countermeasures and tension. The severity of this dilemma depends on the perceived offence–defence balance: when defence dominates, security is easier to sustain; when offence dominates, mistrust prevails.

Finally, the balance-of-power logic underscores reliance on external alignments to offset threats. For smaller powers, alliances with stronger states are vital. Israel’s reliance on the United States to guarantee its “qualitative military edge” exemplifies this mechanism.

Israel’s Defensive Realist Core

Israel’s security strategy has long embodied the logic of defensive realism. At its core lies a doctrine of deterrence based on the conviction that survival depends on maintaining a qualitative military edge over adversaries. Rather than pursuing conquest, Israel has sought military superiority sufficient to dissuade aggression. This orientation is reflected in its layered missile defence systems—Iron Dome and David’s Sling—which neutralise threats across multiple ranges, reassuring the Israeli public while signalling to opponents that the costs of attack outweigh any possible gains.

A central pillar of this deterrent posture is Israel’s policy of nuclear opacity, often termed the “bomb in the basement.” Though never formally acknowledged, Israel is widely believed to possess between 80 and 200 nuclear warheads. This ambiguity serves as existential insurance: it deters adversaries from contemplating Israel’s destruction while avoiding the escalation that an overt declaration might trigger. As Shai Feldman argues, opacity grants Israel a distinct form of strategic stability—reassuring allies while preventing immediate countervailing responses from regional rivals.

Defensive realism also underscores the value of external balancing. Israel’s enduring alignment with the United States exemplifies this approach. Since the 1970s, Washington has guaranteed Israel’s qualitative military edge through advanced weaponry, financial aid, and diplomatic backing. This partnership deters regional challengers and situates Israel within a broader balance-of-power structure in which American presence acts as a stabilising anchor.

Simultaneously, Israel has pursued selective accommodation with former adversaries, consistent with defensive realist reasoning. The peace treaties with Egypt (1979) and Jordan (1994) removed two immediate conventional threats to Israel’s existence. More recently, the Abraham Accords normalised relations with Gulf states such as the UAE and Bahrain, further reducing the likelihood of multi-front war. These agreements reflect an understanding that balance can be achieved not only through military deterrence but also through pragmatic diplomacy.

Together, deterrence doctrine, nuclear opacity, U.S. alliance, and selective accommodation have proven highly effective against state-on-state invasion. Since the Yom Kippur War of 1973, Israel has not faced a full-scale conventional attack, demonstrating that defensive realism, when implemented through both military strength and diplomatic engagement, can indeed preserve survival in a hostile regional order.

The Iran-Centred Security Dilemma

Among Israel’s adversaries, Iran represents the most consistent and existential challenge, shaping Israeli security doctrine for decades. The interaction between the two states illustrates a classic security dilemma: defensive measures by one are interpreted as offensive threats by the other, leading to cycles of escalation. Israel views Iran’s regional strategy, centred on ballistic missile development and the mobilisation of proxy forces such as Hezbollah, Hamas, and the Houthis, as an existential danger. Iran, in turn, sees Israel’s nuclear opacity, U.S.-backed qualitative military edge, and history of pre-emptive strikes as evidence of aggressive intent.

The 7 October 2023 Hamas attacks on southern Israel demonstrated the vulnerability of Israel’s deterrence posture against non-state actors backed by Iran. Despite its sophisticated military capabilities, Israel was unable to prevent the killing of more than 1,200 civilians and soldiers, the capture of hostages, and the temporary overrunning of towns near Gaza. For Tehran, the attacks validated its long-standing investment in asymmetric strategies designed to bypass Israel’s technological superiority. For Israel, however, the shock was not merely tactical but strategic: deterrence had failed against an adversary supported by Iran, exposing the limitations of a purely defensive posture.

The escalation intensified with Iran’s unprecedented direct strike on Israel on 13–14 April 2024. Over 300 projectiles—including drones, cruise missiles, and ballistic missiles—were launched at Israeli territory, marking the first overt Iranian attack on the state itself. Although the vast majority were intercepted by Israel’s multilayered defence systems, aided by the United States, the United Kingdom, France, and Jordan, a handful penetrated defences, striking military sites. This assault demonstrated both the effectiveness and the limits of defensive realism: while Israel’s survival and critical infrastructure remained intact, the attack broke a long-standing taboo, proving that even a nuclear-armed state with advanced defensive systems could not achieve absolute protection.

In June 2025, the confrontation escalated into open war. Israel launched extensive strikes inside Iran, targeting nuclear facilities, military bases, and senior officials. These attacks aimed not only at delaying Iran’s nuclear programme but also at weakening the regime’s ability to project influence across the region. Iran retaliated with waves of missile and drone strikes, inflicting damage but failing to alter the balance of power. The United States, while initially cautious, became increasingly involved in air and missile defence, underlining the structural dependence of Israel on its patron. This episode highlights the precarious balance between deterrence and escalation: Israeli pre-emption achieved short-term operational gains but risked entangling its U.S. ally more deeply, and revealed that security could not be guaranteed without the risk of spiralling conflict.

The behaviour of the broader “Axis of Resistance” further illuminates the dynamics of the security dilemma. Hezbollah, heavily degraded by years of Israeli strikes, mounted limited operations but avoided a full-scale war, likely due to both Iranian restraint and Lebanese domestic constraints. Iraqi militias, by contrast, largely sat out the 2025 conflict, a decision shaped by Baghdad’s desire to avoid U.S. retaliation and by Tehran’s calculation that opening multiple fronts might overextend its resources. This selective engagement underscores the complexity of deterrence in a networked conflict environment: while Israel’s defensive posture may dissuade some actors, it cannot eliminate threats across the spectrum of Iranian proxies.

Stephen Walt’s recent assessment reinforces this conclusion. Israel’s far-reaching operations across Gaza, Lebanon, Syria, Yemen, and Iran might suggest an emerging regional hegemon, yet Walt argues that such a label is misplaced. Israel’s superior military capabilities and U.S. backing ensure it can strike widely, but Iran’s continued resistance—and its ability to retaliate significantly even after suffering heavy losses—demonstrates that Israel cannot compel deference from regional rivals. For Walt, Israel’s pursuit of dominance through offensive realist strategies has generated only temporary gains while perpetuating long-term insecurity. A true hegemon, such as the United States in the Western Hemisphere, enjoys “free security” and need not fear significant threats; Israel remains far from such a position.

The Iran-centred security dilemma thus exposes the limits of defensive realism in the Israeli case. Defensive strategies—nuclear opacity, missile defence, and external balancing with the United States—have secured state survival but have not prevented spirals of escalation. Conversely, offensive strategies, such as pre-emptive strikes inside Iran, have yielded tactical benefits but provoked renewed retaliation, sustaining rather than resolving insecurity. The cycle reveals that security cannot be “guaranteed” under conditions of mutual suspicion, asymmetry, and networked proxy warfare. Israel’s experience with Iran demonstrates that in a multipolar regional system, defensive realism provides survival but not tranquillity; it forestalls destruction but fails to deliver lasting peace.

Offensive Realist Slippage and Its Costs

Although Israel’s security doctrine is grounded in defensive realism, its conduct often drifts towards offensive realist strategies. This is most evident in its record of pre-emptive and denial strikes, such as the 1981 bombing of Iraq’s Osirak reactor and the 2007 attack on Syria’s al-Kibar facility. These operations delayed adversaries’ nuclear ambitions and enhanced Israel’s image of resolve and deterrence. Yet they also reinforced the perception that Israel would not accept any alteration to the regional balance of power, prompting rivals to adopt asymmetric and clandestine responses.

This trajectory reached its peak in 2025, when Israel expanded denial operations deep into Iranian territory, striking nuclear sites, military bases, and senior officials. These attacks exemplified Mearsheimer’s offensive realism: when opportunities emerge, states exploit them to weaken rivals and consolidate relative power. In the short term, Israel demonstrated operational superiority and inflicted significant losses on Iran. Yet the strikes triggered successive Iranian retaliations and risked deeper U.S. entanglement—illustrating how pre-emption can entrap allies and exacerbate escalation.

Measured against key security benchmarks, outcomes remain mixed. State survival is secure, protected by nuclear opacity and sustained U.S. backing. Inter-state deterrence has largely endured—no Arab state has launched a full-scale war since 1973, and even Iran’s 2025 responses stayed limited. However, escalation control has proved fragile. Each offensive episode widened the conflict, multiplied regional risks, and undermined the long-term stability that defensive realism seeks to preserve.

The repercussions extend beyond the battlefield. Repeated wars have strained Israeli society, with civilian casualties and the psychological burden of constant mobilisation. Economically, the 2025 war disrupted regional integration efforts, including projects under the Abraham Accords. Diplomatically, Israel’s legitimacy has eroded: human rights organisations accused it of genocide in Gaza, and global opinion turned sharply negative. These reputational costs have diminished international support, leaving Israel increasingly isolated even as its military edge persists.

Stephen Walt underscores the futility of such offensives. Despite advanced capabilities and U.S. patronage, Israel cannot attain the “free security” of a hegemon. Iran, Turkey, and resilient non-state actors continue to impose costs, while U.S. involvement risks overextension. Israel’s pursuit of dominance has instead produced balancing and entrapment, deepening rather than resolving insecurity.

Defensive Realism and Its Limits in the Israeli Case

The Israeli experience suggests that defensive realism can provide survival but cannot guarantee security. Since 1973, Israel has avoided full-scale conventional invasion by neighbouring states, demonstrating the effectiveness of deterrence, nuclear opacity, and external balancing through the United States. At this level, defensive realism has “worked”: the state endures, retains a qualitative military edge, and prevents adversaries from contemplating outright conquest.

Yet security, understood more broadly as protection from sustained threats and societal vulnerability, has not been secured. Israel’s confrontation with Iran and its proxies exposes the limits of a purely defensive approach. The 7 October 2023 Hamas attack shattered the perception of deterrence against non-state actors. The April 2024 Iranian missile salvo demonstrated that even with sophisticated multilayered defences, no system can guarantee immunity. The 2025 Israeli strikes deep inside Iran revealed how denial operations, though tactically successful, risk escalation spirals, entrapment of allies, and further retaliation. Each episode shows that Israel’s reliance on offensive realist measures to supplement defence has intensified the very security dilemma it seeks to manage.

The policy lesson is that pure defence is insufficient, but pure offence is self-defeating. Effective security in this context depends on a composite approach: denial capabilities to blunt attacks, damage-limitation strategies to reassure the public, carefully bounded coercion against adversaries, and diplomatic off-ramps to prevent endless escalation. Israel’s experience thus illustrates both the utility and the limits of realism: survival is achievable, but security is always relative, fragile, and contingent.

More broadly, the case contributes to realist theory by showing how small powers with nuclear opacity operate under conditions of proxy warfare and missile-age deterrence. It highlights the paradox that military supremacy does not translate into lasting safety, and that in an anarchic order, even survival does not equal security.

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News / Primary Sources (included since you cited them in footnotes):

Al Jazeera. “Iran Launches Massive Drone and Missile Attack on Israel.” 14 April 2024.

BBC News. “Iranian Strikes on Israel: Coalition Defence Intercepts Majority.” 15 April 2024.