TORONTO — The key question about Iran’s energy-export terminal on Kharg Island is not whether the United States can seize or disable it. Of course it can. The real issue is what happens afterward, when the conditional logic that the US has applied to its alliances begins to shape allied behavior in turn. When allies’ behavior can no longer be assumed, American power becomes more constrained. The key variable is no longer what the US can do, but what costs others will be willing to bear. American primacy rested on a simple bargain—pay more, decide more, and allies follow. That bargain is broken.

 

Such is the problem now confronting President Donald Trump’s administration. Kharg Island looks like the kind of target the world’s strongest military should be able to turn into leverage with relative ease. But difficult trade-offs would soon follow. Seizing and holding it would impose a sustained burden that allies would be expected to help carry, whereas destroying it would deliver a sharper, escalatory blow whose costs would be immediate, unevenly distributed, and concentrated among the partners most vulnerable to energy shocks. Both options rely on allied participation in different forms, and neither can be taken for granted.

 

Obviously, any serious disruption would cascade through global energy markets, tightening supply, driving up prices, and increasing shipping and insurance risks. But much of that sensitivity reflects the vulnerability of the Strait of Hormuz, a chokepoint for a significant share of global oil flows, where even limited disruption can affect supply expectations far beyond any single facility.

 

Kharg Island, by contrast, handles roughly 90 per cent of Iran’s own oil exports (more than one million barrels per day), concentrating a significant share of supply at a single, exposed point. That concentration makes the island immediately visible to markets, which have already responded to the risk of escalation despite the continued flow of exports. War-risk premiums are increasing for tankers moving through the Gulf, raising the cost of transit even without sustained physical damage. Insurers are restricting or withdrawing coverage, and some shipments are being delayed or diverted, tightening effective supply at the margin and adding upward pressure on prices even before any sustained supply loss.

 

In the event of a disruption at Kharg Island, these effects would not be confined to Iran. They would be felt acutely in economies that depend on imported energy, most of which are already struggling to manage inflation and weak growth, with limited political room to absorb further shocks. Recent tanker data show how quickly these pressures fragment, with rates splitting sharply across allied routes by early March, revealing a fundamental asymmetry in how the shock is transmitted. For governments in Europe and across Asia, higher energy costs translate directly into domestic pressure, because they affect industrial competitiveness, household budgets and political stability.

 

In earlier periods, those costs might have been willingly absorbed within the US alliance network. Though they would not have been evenly distributed, they would have been accepted as part of a shared strategic effort. Not anymore. What has changed is not simply the distribution of costs, but expectations about who will bear them, and uncertainty about whether they will be shared at all.

 

For years now, the US has treated alliances less as durable commitments than as arrangements to be publicly questioned and renegotiated. There have been repeated disputes over burden sharing within NATO, with US officials openly questioning Article 5 (mutual-defense) commitments and publicly disparaging allied governments. As a result, security guarantees have become contingent commitments.

 

This change has prompted allies to hedge their bets by not automatically aligning themselves with the US during crises. The cumulative effect has been a shift in how allies think about what they can rely on in crises. Arrangements that were once organized around standing commitments are increasingly taking the form of situational coalitions. While selective autonomy on the part of US allies can work in some cases, if it becomes the default, coordination will splinter, producing uneven responses from one crisis to the next.

 

That is what we are now seeing. The shift to greater conditionality is shaping how all governments respond to geopolitical developments, with some US allies already limiting their involvement as the risks of escalation grow. In reducing their exposure, they weaken the expectation of coordinated allied action.

 

By concentrating both the potential benefits and the costs of action, Kharg Island brings this dynamic into sharper focus. Seizing it would increase pressure on Iran, but it would also redistribute strain across the coalition needed to sustain that pressure. The same move that generates leverage introduces risk, and that risk is distributed across the partners expected to bear it.

 

More broadly, moving from a system of assumed alignment to one that must be negotiated raises the political cost of collective action and weakens its strategic effect. Conditional alliances will not end all cooperation, but they make it more difficult to translate alignment into power on a predictable basis.

 

That is why Kharg Island—the “forbidden island”—matters. It is important not because it lies beyond American reach, but because it is tempting the US to pursue a course of action with consequences others may not be willing to shoulder. The US military can seize the island, but it cannot compel others to share in whatever outcome follows. The old message was clear: contribute more or the security guarantee weakens. The new one is just as stark: without agreement on the mission, allied support weakens.

 

Carla Norrlöf is Professor of Political Science at the University of Toronto.