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Iran’s deterrence doctrine: From horizontal resilience to vertical strength

January 15, 2025 at 2:18 pm

Heavy weapons, including ballistic missiles, air defence systems and unmanned aerial vehicles, are displayed at Baharestan Square in Tehran, Iran on September 25, 2024 [Fatemeh Bahrami/Anadolu via Getty Images]

Iran is moving from a horizontal to a vertical stance in its deterrent strategy, which is a major change. The decrease in its regional influence and the waning effectiveness of its proxy networks have forced a strategic recalibration, which is reflected in this change. Iran has historically projected strength outside of its boundaries using a horizontal deterrent strategy known as “forward defence” or “mosaic defence”, which included the employment of proxies, ballistic missiles, naval guerrilla tactics and cyber technologies. It aimed to neutralise threats before they reached its territory by keeping its defensive depth. Recent events, however, have highlighted this policy’s shortcomings, leading to a shift toward a more centralised and technologically driven deterrence posture.

The weakening of horizontal deterrence

Iran’s horizontal deterrence policy has encountered increasing difficulties in recent years. The efficiency of its proxy networks has been undermined by the severe attrition they have experienced because of ongoing battles, especially in Gaza and Lebanon. The insufficiency of Iran’s conventional deterrent weapons against technologically superior foes was exposed by its missile strikes on Israel in April 2024. Iran’s traditional strategy has been further stressed by changing regional dynamics, such as an increasingly forceful Israeli posture and increased US military involvement. Iran’s forward defence strategy is therefore widely seen as unable to counter modern threats.

A combination of long-term security imperatives, foreign challenges and internal dynamics is driving Iran’s strategic pivot to vertical deterrence. Tehran has been compelled to reevaluate its reliance on its proxy networks for forward defence due to their declining effectiveness because of regional instability and the crises in Gaza and Lebanon.

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Furthermore, the necessity for technological modernisation has been highlighted by Israeli military operations that have revealed serious weaknesses in Iran’s solid-fuel missile production capabilities and air defence systems. Despite budgetary restraints and a heavily sanctioned economy, Iran has dramatically raised its military budget for the year 1404 (March 2025–March 2026) by 200 per cent, prioritising the development of modern defence technologies, including drones, air defences and missile systems. This investment demonstrates a dedication to improving its strategic posture and resolving technology shortcomings. Even if Iran’s leadership continues to formally reject any plans to weaponise the country, continuous internal discussions about nuclear deterrence raise the possibility of a change in strategy. All these elements work together to highlight Iran’s resolute shift toward a vertically integrated defence policy meant to protect its interests as a nation in the face of growing regional and international threats.

Implications of the strategic shift

Iran’s move from horizontal to vertical deterrence has significant ramifications for regional and international security, and it may have a cascade of destabilising consequences. Iran’s developments in drones, missiles and nuclear weapons might create a security conundrum in the region, forcing nearby nations to step up their own defence initiatives and escalating the Middle East’s arms race. Conflict risks would increase because of this spread of military technologies since nations like Saudi Arabia, the United Arab Emirates and others would try to offset Iran’s increasing military might. Iran’s already troubled economy could be made worse by its pursuit of superior military weapons, especially its nuclear hedging approach. Increasing defence spending might increase Tehran’s diplomatic isolation, invite further international sanctions and take funds away from urgent domestic needs.

The ambiguity surrounding Iran’s nuclear intentions also undermines global nonproliferation efforts, as the international community remains uncertain about Tehran’s true nuclear ambitions. By maintaining its nuclear programme on the edge of weaponisation, Iran raises concerns of a potential regional nuclear arms race and challenges the global nonproliferation framework, making it harder for diplomatic solutions to prevail. This evolving situation demands careful attention from both regional actors and the international community to mitigate the risks of escalation and prevent the further destabilisation of the region.

The role of Shia ideology

Iran’s Shia religious beliefs, which combine strategic goals with theological explanations, have a significant impact on its deterrent policy. Iran is able to give regime survival and national security first priority because of the ideology of Velayat-e-faqih, which gives the governing jurist flexibility in coordinating strategic decisions with Islamic precepts. Its use of asymmetric warfare techniques, such as ballistic missiles, drones and proxies, reflects this flexibility and is consistent with Shia beliefs about defending Shia people around the region and against oppression. The state’s dedication to defending allies like Hezbollah and Iraqi militias is demonstrated by its regional dominance, which is embodied in the “Shia Axis”.

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Iran’s changing strategic calculation is made considerably more complex by Donald Trump’s return to the presidency in 2025, which could hasten Iran’s transition to vertical deterrence. Tehran is under increased pressure due to the expected return of “maximum pressure” measures, including harsher economic sanctions and steadfast support for Israeli military operations. Iran may accelerate its vertical deterrence measures in response to these outside pressures and the alleged danger of Israeli or American strikes on vital facilities.

Pursuing a nuclear “threshold state” status, in which Iran retains sophisticated nuclear capabilities without completely weaponising, is one possible reaction. This would maintain strategic ambiguity while preventing overt international reprisal. Hardline groups within Iran, however, might push for going over the threshold to build a nuclear weapon, claiming that it is the only reliable deterrence against the United States and Israel’s increasing hostilities. At the same time, Tehran may use its sophisticated nuclear programme as leverage in diplomatic negotiations, requesting concessions or security assurances that lessen outside pressure. Iran’s will to protect its national security and navigate a more hostile geopolitical landscape during Trump’s second term is reflected in this multifaceted strategy.

Domestically, Iran faces the challenge of balancing its military investments with the economic strain caused by sanctions and internal dissatisfaction. Increased defence spending on missile and nuclear technologies may further stretch the country’s resources, aggravating domestic economic hardships and potentially spark unrest. Iran’s decisions in the coming months will have lasting implications for the Middle East’s geopolitical dynamics, and the international community must act decisively to address the underlying causes of Iran’s strategic shift while promoting regional and global stability.

The views expressed in this article belong to the author and do not necessarily reflect the editorial policy of Middle East Monitor.