The messy crisis in the Strait of Hormuz has clarified how power works in the 21st century.
It reminds us that the greatest long-term threat to the United States is not China’s military buildup or Russian aggression, but the gradual fragmentation of the alliance system that has underwritten its global leadership since World War II.
For eight decades, this strategic asset has mattered more than raw military power, because no US rival has been able to match it.
With more than 50 treaty allies and formal security partners, the US built the first truly global security system in history.
China has trading partners but only one security ally (North Korea), and Russia’s five allies are bound by dependence and coercion.
The US alone leads a worldwide coalition of countries that have, for generations, voluntarily chosen to tie their security to it.
To be sure, several presidents, especially Donald Trump, have voiced concerns about the alliance system’s costs. But what they see as a liability has repeatedly enabled the US to mobilize coalitions when crises erupt.
In 1991, for example, the US assembled a vast multinational force to expel Iraqi troops from Kuwait. NATO allies, Arab partners, and Asian states contributed forces, funding, and logistics.
Even during the far more divisive Iraq war in the 2000s, the US was able to attract partners.
Four countries participated in the initial invasion, and nearly 40 deployed troops at some point during the war. Many contributions were small, with some consisting of a few hundred soldiers or specialized support units.
But the political and military reality remained the same: even in controversial wars, US power operated through coalitions rather than unilateralism.
The Strait of Hormuz
The contrast with the present moment is striking. As tensions rise around Iran and oil prices spike, the Trump administration has pleaded with allies to help secure shipping through the Strait of Hormuz, one of the most important waterways in the global economy.
Nearly one-fifth of the world’s oil and liquefied natural gas passes through the narrow channel connecting the Persian Gulf to international markets, giving allies a direct stake in keeping it open.
Yet the response from America’s security partners has been muted, hesitant, or negative. Several major allies – including Spain, Italy, and Germany – have rejected participation.
Allies that once mobilized alongside the US now appear increasingly reluctant to bear security risks under its leadership
Australia has said it will not send ships, while Canada has ruled out offensive operations. France, Japan, and South Korea have not committed warships to the US-led mission.
Britain says it is discussing options with partners, but it has not yet announced a deployment.
The pattern is unmistakable: Allies that once mobilized alongside the US now appear increasingly reluctant to bear security risks under its leadership.
Part of this hesitation reflects the cumulative cost of years in which Trump and his MAGA followers have publicly disparaged allies, questioned security commitments, and treated the alliance system as a burden rather than America’s most valuable strategic asset.
A deeper shift is underway
Disagreements within alliances are not new. NATO has survived divisive crises, from the Suez conflict in 1956 to the Iraq war and the first Trump administration’s withdrawal from the Iran nuclear deal.
But this time, the story is not limited to allied reluctance. A deeper shift is underway.
Key partners such as France and Italy have reportedly begun exploring direct discussions with Iran to secure safe passage for their own commercial shipping through the Strait of Hormuz.
Although such talks remain tentative, the fact that they are even happening is historically significant.
Instead of coordinating a collective response through the alliance system, several allies are exploring independent arrangements with the very state the US has gone to war against
Energy markets help explain the urgency. Oil prices have surged above $100 per barrel, and European gas prices have risen sharply as shipping collapses.
European governments fear that a prolonged closure of the strait could deepen the economic strains already weighing on their economies.
But instead of coordinating a collective response through the alliance system, several allies are exploring independent arrangements with the very state the US has gone to war against.
Alliances rarely collapse abruptly
For decades, US leadership discouraged precisely this behavior, because it was based on the understanding that separate bargains with adversaries would erode the cohesion that alliances require.
Alliances rest on collective security, with members confronting threats jointly.
Alliances rarely collapse abruptly. More often, they erode gradually as members begin hedging their security outside the system
Once governments begin negotiating their own carve-outs with adversaries, the alliance ceases to function as a coordinated security network and becomes a loose aggregation of national strategies.
Alliances rarely collapse abruptly. More often, they erode gradually as members begin hedging their security outside the system.
If European states succeed in negotiating separate guarantees with Iran rather than acting through the alliance system, the implications will extend far beyond the Persian Gulf.
Such an outcome would strike at the heart of American power and could mark the beginning of a broader breakdown in the US-centered global security architecture.
That architecture took generations to build. Security fragmentation could dismantle it far more quickly.
And make no mistake: if the US loses the alliance system that amplifies its power, it will face not just a less hospitable world, but an unfamiliar one, no longer shaped by the hegemonic power that most Americans alive today have always taken for granted.
Carla Norrlöf is Professor of Political Science at the University of Toronto.
