Why would a weakened state, facing worsening strategic conditions, respond to an attack by making war more difficult rather than easier to contain? The literature and historical record show that states under attack often strike back. However, Iran’s case shows a puzzle. After the killing of senior leaders and the erosion of the Axis of Resistance, Iran might have been expected to act more cautiously. Instead, the regime widened the conflict across the Middle East and closed the Strait of Hormuz. This marked a striking departure from the more contained response it had employed during the 12-Day War. Existing literature interprets Iran’s offensive shift as a move from deterrence by denial to deterrence by punishment. This article agrees that Iran turned to punishment; however, it argues that conventional understandings of punishment, as the threat of controllable cost, cannot account for the behaviour of the Islamic Republic in 2026. Drawing on Schelling’s theory of brinkmanship, the article develops the concept of deterrence by uncontainability: a strategy in which a state gains leverage by making further escalation appear difficult to contain. In Iran’s case, the coercive threat was not simply that it would impose limited retaliatory costs, but that continued attacks could widen the war across the region, disrupt energy flows, and generate risks beyond the adversary’s control. Iran’s leverage came less from controlling escalation than from convincing its adversaries that escalation might become uncontrollable. Within a neoclassical realist framework, the article treats Iran’s deteriorating strategic position as the structural predicament that made deterrence its central problem, while locating the decision to respond with uncontainable rather than contained escalation in the leaders' choices. It tests this through a structured comparison of the 2026 and 2025 wars, using process tracing and Persian language sources.
