The St Andrews professor’s analysis of American alliance decline is rigorous, well-sourced, and accidentally devastating to his own argument
I want to be careful here, because this is a writer I take seriously. Phillips P. O’Brien—the Chair of Strategic Studies at the University of St Andrews and author of War and Power: Who Wins Wars and Why—published a piece this weekend titled “Yeesh, Who Would Have Thought That Allies Actually Mattered?” in which he argues, with characteristic rigor, that Trump has “set out to explode a bomb under the existing US alliance structure” and that this explains why the president’s calls for help in the Strait of Hormuz are going unanswered. He calls Trump “an accelerant of US decline.” I discussed O’Brien’s earlier work on my podcast Strategic Clarity in a January episode that generated what I considered a productive amount of engagement, and I have enormous respect for his scholarship. But I believe—and this is where institutional analysts like O’Brien consistently fall short—that he’s looking at the Trump alliance crisis through the wrong framework entirely.
O’Brien’s central thesis is simple: alliances win wars, great powers do not. He’s been writing about this for years. His earlier piece, subtitled “Alliances Win Wars, Great Powers Do Not,” argued that the U.S.-led alliance system has been the primary engine of American global power since World War II, and that dismantling it is an act of strategic self-harm. On the surface, this is unassailable. I’ll go further—it’s the kind of analysis that makes people who run one-person think tanks out of their home offices nod along and feel validated. I would know.
The Trump Alliance Crisis Through the Realist Lens
But here’s what O’Brien can’t see from his perch in Scotland: the alliance system he’s mourning was already dead. It just hadn’t stopped breathing.
Look at what happened this weekend. President Trump called on France, the United Kingdom, Japan, South Korea, China, and other nations to send warships to help secure the Strait of Hormuz—a waterway through which 20% of the world’s oil flows, including enormous volumes bound for the very countries he’s asking for help. FRANCE 24’s Oliver Farry laid out the response in a segment worth watching in full:
France said non. Japan called the threshold for deployment “extremely high.” Australia said it wouldn’t send ships. Britain is hedging. Germany’s foreign minister called the idea of extending the EU’s naval mission to Hormuz “not effective.” A senior Japanese policy adviser said the situation “must be considered with great caution,” which, for anyone who has studied the diplomatic lexicon, is the Japanese equivalent of hanging up the phone.
O’Brien looks at this and sees the collapse of an alliance structure. I look at this and see an alliance structure that was never load-bearing.
An Alliance Audit, Whether Anyone Wanted One or Not
This is the part where O’Brien’s analysis gets genuinely interesting—and where he veers off course. He writes that Trump has been “blasting away” at these alliances since retaking office. The Greenland threats, the NATO ultimatums, the tariffs on European goods, the insults to Prime Minister Starmer, the treatment of the liberal world order as something to be dismantled rather than maintained. All true. All documented. I’ve been tracking this on my Foundation’s research dashboard since January 2025, and the data is unambiguous.
But O’Brien draws the wrong conclusion. He thinks Trump destroyed something functional. What Trump actually did was conduct an alliance audit—the most aggressive in postwar history—and the results are now public. These nations won’t send warships to the Strait of Hormuz not because Trump insulted them, but because they were never going to. They didn’t have the capability, the political will, or the strategic culture to act as genuine security partners. They had the habit of being defended.
I made a similar argument on Strategic Clarity last month—Episode 83, “Alliance Architecture in the Post-Hegemonic Transition”—and I think the point holds. You can read O’Brien’s work, as I have, and come away with the impression that the postwar alliance system was a marvel of cooperative security. But you can also read it and notice that the United States was paying for approximately everything while its allies maintained defense budgets calibrated for peacetime, militaries designed for parades, and foreign policies optimized for disapproval from a safe distance.
The Freeloading Revelation
Consider the numbers. France’s entire aircraft carrier fleet consists of one vessel, the Charles de Gaulle, which is currently not in the Strait of Hormuz. Britain’s Royal Navy has been in a state of managed decline for decades; the HMS Prince of Wales was being prepared for possible deployment until the president told them not to bother, having already won the war. Japan’s pacifist constitution limits its ability to participate in combat operations abroad. Germany—the largest economy in Europe—just said it won’t participate in any military effort to keep the strait open “as long as this war continues.”
O’Brien calls this the consequence of Trump’s alliance destruction. I call it the first honest assessment of allied capability and willingness in seventy years. These are the same nations whose combined naval power O’Brien celebrates as proof that the alliance system “works.” But when the system is asked to actually work—to send ships, to share risk, to escort oil tankers through a strait that fuels their own economies—the answer from every direction is some polished version of “not our problem.”
I discussed this precise scenario in my master’s thesis on NATO expansion. The framework was different, of course—I was writing about Article 5 contingencies in the Baltics, not Iranian closure of a shipping lane—but the structural dynamic is identical. Alliance commitments are not alliance capabilities.
What O’Brien Accidentally Proves
Here is the irony that I suspect O’Brien would reject but that his own data supports: if alliances truly do win wars—and I believe they do—then the United States needs allies who are willing to fight, not allies who are willing to attend summits. Trump’s approach has been, admittedly, unorthodox. Threatening NATO’s future if allies don’t help open the strait is, shall we say, not how they taught it at Georgetown. But it has produced something no amount of diplomatic niceties could: clarity.
We now know exactly what these alliances are worth in a crisis. The answer, measured in warships dispatched to the Strait of Hormuz, is zero.
And here is the detail that I think should concern O’Brien more than anything Trump has done: as O’Brien himself noted in a recent conversation with Paul Krugman, Ukraine has provided more military aid to the United States in 2026 than the United States has provided to Ukraine. Ukrainian drone teams are now operating in Qatar, Saudi Arabia, the UAE, and at a U.S. base in Jordan, deploying battle-tested interceptor technology that the administration initially rejected. Meanwhile, Chinese-chartered ships are transiting the Strait of Hormuz unmolested, broadcasting their identity in English and trading Iranian oil in yuan.
Ukraine—a nation the U.S. has essentially abandoned—is doing more for American security in the Persian Gulf than France, Britain, Japan, and Germany combined. If that doesn’t tell you something about the state of the alliance system O’Brien is eulogizing, I don’t know what will.
The Hard Question
I have been studying alliance dynamics for nearly two decades, and I will say something that will make me unpopular at the conferences I occasionally attend: O’Brien’s analysis is technically correct and strategically irrelevant. Yes, alliances matter. Yes, Trump has damaged them. But damaged alliances that produce warships are worth more than pristine alliances that produce press releases. And right now, the nations that benefited most from eight decades of American security guarantee are responding to the first real test of that guarantee by checking their constitutions for escape clauses.
Trump didn’t destroy the alliance system. He revealed it. The fact that the revelation is ugly doesn’t make it wrong.
I plan to address this in greater depth on an upcoming episode of Strategic Clarity. I’ve reached out to two former ambassadors for comment. Neither has responded yet, but the invitation remains open.
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