WASHINGTON, DC – 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