The End of the Unipolar Moment: How the Hormuz Crisis Marks a Point of No Return for American Global Leadership

The phrase "unipolar moment" was coined by the American commentator Charles Krauthammer in 1990, describing the period of absolute American strategic dominance that followed the Cold War's end — a world in which no other power could counterbalance U.S. military and economic weight, and in which American preferences could shape global outcomes across virtually every domain. Krauthammer himself warned that the moment was temporary, that the structural conditions producing it would erode, and that American policy needed to use the window wisely while it lasted. The window lasted longer than most structural realists expected. The Hormuz crisis of 2026 may represent its definitive close.

The Markers of Decline

Hegemonic decline is rarely a single dramatic event — it is an accumulation of evidence, each piece of which could be explained away individually, but whose cumulative weight eventually becomes undeniable. The past two weeks have produced an unusually compressed accumulation of such evidence. The world's most powerful military has been unable to reopen a fifty-kilometre waterway through three weeks of sustained effort. The United States' closest European allies have publicly refused requests for military assistance from a sitting U.S. president, citing a war they were not consulted about and do not consider legitimate. The global south — as represented in the UN General Assembly resolution calling for an immediate ceasefire — has made clear that it does not regard American military action as carrying the legitimacy it once did. And China has positioned itself as the responsible adult in the room while the United States manages a crisis of its own creation.

What American Leadership Actually Rested On

American global leadership was never simply about military power — though military power was its essential foundation. It rested on a combination of material capabilities, institutional relationships (NATO, the UN Security Council, the IMF and World Bank, the WTO), ideological appeal (the liberal international order as a genuinely attractive model for development and governance), and legitimacy — the widespread acceptance that American leadership, however self-interested, broadly served global stability and prosperity.

Each of these foundations has been eroding for a decade, accelerated by domestic political developments that have made the United States a less consistent and less predictable participant in the international institutions it built. The Trump administration's first term demonstrated that American commitments could be abandoned, alliances could be scorned, and international agreements could be unilaterally withdrawn. The current crisis has added a new data point: that American military action can be taken without allied consultation, at global economic cost, and without the institutional legitimacy framework that previously buffered allied criticism.

The Multipolar Reality

What is replacing American unipolarity is not another hegemon — China is not ready, willing, or able to assume global leadership in the way the United States did after 1945 — but a more genuinely multipolar world in which major regional powers exercise significant autonomy, middle powers assert their interests more boldly, and the global south demands a voice in decisions that affect it. This is a world that is harder to coordinate, more prone to the kind of regional conflicts whose global spillovers the Hormuz crisis exemplifies, and less amenable to the kind of clear ordering principle that characterised either the Cold War bipolar world or the post-Cold War unipolar one.

Managing that transition — from a world America could largely direct to a world it must negotiate — is the defining strategic challenge of American foreign policy for the next generation. The Hormuz crisis has not created that challenge. But it has made it impossible to ignore.