ROBERT A. PAPE is Professor of Political Science and Director of the University of Chicago Project on Security and Threats. He is the author of Bombing to Win: Air Power and Coercion in War.

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FAR HORIZONS

Horizontal escalation occurs when a state widens the geographic and political scope of a conflict rather than intensifying it vertically in a single theater. It is especially appealing as a strategy for the weaker parties in a military contest. Instead of trying to defeat a stronger adversary head-on, the weaker side multiplies arenas of risk—drawing additional states, economic sectors, and domestic publics into the remit of the conflict. Iran cannot defeat the United States or Israel in a conventional military contest. It does not need to. Its objective is to gain greater political leverage.

The strategy of horizontal escalation follows a recognizable pattern. First, Iran has demonstrated resilience. U.S. decapitation strikes intended to paralyze the Iranian military. By launching large-scale retaliation within hours of losing the supreme leader and many senior commanders, Tehran signaled continuity of command and operational capacity.

Second, Iran has widened the conflict well beyond Iranian territory, effecting what scholars call “multiplication of exposure.” Rather than confining retaliation to just Israel, Iran struck or aimed at targets in at least nine countries, most hosting U.S. forces: Azerbaijan, Bahrain, Greece, Iraq, Jordan, Kuwait, Qatar, Saudi Arabia, and the United Arab Emirates. The message was unmistakable: those countries that host American forces would face severe consequences and the war that Israel and the United States started will spread.

Decapitation strikes create powerful incentives for horizontal escalation.

Third, Iran has politicized the conflict through its strikes. Iran’s retaliation has resulted in the closure of airports, the burning of commercial property, the killing of foreign workers, and the disruption of energy and insurance markets. Gulf leaders have been forced to reassure foreign investors and tourists. The war has migrated into boardrooms and parliamentary chambers. In the United States, the widening scope of the war has alarmed members of Congress. Numerous actors have now entered the conflict, each pursuing distinct interests, none fully coordinated, and all capable of altering the trajectory of escalation beyond Washington’s control.

The final dimension of Iran’s strategy is time. The longer multiple states feel pressure, the more that politics both within and among regional states can intensify the conflict. Without a version of NATO in the Middle East or a single American general effectively running the military operation for all the countries targeted by Iran, there is a high risk of wires getting crossed. U.S. officials have, for instance, floated the idea of stoking an ethnic rebellion in Kurdish parts of Iran to help target the Islamic Revolutionary Guard Corps. But that might provoke responses from Iraq, Syria, and Turkey, countries that would not welcome a powerful Kurdish insurgency in the region. The recent downing of three U.S. jets in a friendly-fire incident over Kuwait also illustrates the logistical and coordination problems that bedevil any attempt to fend off Iran’s escalation in the Gulf.

Iran’s foreign ministry reinforced this logic publicly, framing the missile barrages as legitimate responses against all “hostile forces” in the region. The phrasing has widened responsibility for the attack on Iran beyond Israel and the United States to encompass the broader U.S.-aligned order in the Gulf. Although Iranian President Masoud Pezeshkian has apologized to Gulf neighbors for the attacks, the installation of a new supreme leader aligned closely with the Revolutionary Guard suggests that such gestures are tactical rather than a signal that Tehran intends to abandon its strategy of horizontal escalation. Fundamentally, Iran’s horizontal escalation is a political strategy. It plays directly to the audience that Iran seeks to persuade: the Muslim populations across the region that may not be ideologically aligned with Iran but are generally poorly disposed toward Israel.

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