Alright, here's what Daniel sent us. He's asking about the US blockade of the Strait of Hormuz — which, as of this morning, is actually happening. Trump announced it on Truth Social. Blockade of ships entering and leaving Iranian ports, effective ten AM Eastern today. The strait handles roughly twenty percent of global oil supply daily, so Daniel wants us to dig into two things: the history of naval blockades as a method of war, and what we actually expect to unfold over the next twenty-four hours. No pressure.
Herman Poppleberry, by the way, for anyone just finding us. And yeah — this is not a drill. This is one of those episodes where we're recording against a live situation.
By the way, today's script is powered by Claude Sonnet four point six, so if anything sounds unusually well-informed, blame the AI.
We should say upfront: the blockade was set to begin at ten AM Eastern. As we're recording this, we don't have confirmed reports of first contact or any incident. But Iran has explicitly threatened retaliation against any port in the Persian Gulf or Sea of Oman. So the next twenty-four hours are genuinely unpredictable.
Let's start with the history, because I think context matters enormously here. When Trump uses the word "blockade" — and he did use that word explicitly — that's not a neutral choice. Kennedy in 1962 went out of his way to call his action a "quarantine" precisely to avoid the legal implications of the word blockade. Trump just said blockade. What does that actually mean legally?
Under international law, a blockade is a recognized belligerent operation — meaning it's a recognized act of war. The foundational document is the Declaration of Paris from 1856, which came out of the Crimean War negotiations. The key principle it established was that a blockade must be effective to be legally binding. A so-called paper blockade — declared but not actually enforced — has no legal standing. You can't just announce a blockade and expect other nations to honor it. You have to physically enforce it.
So the US saying it will enforce this impartially against vessels from all nations — that's actually doing legal work. That's them trying to satisfy the "effective" requirement.
That's part of it. The other thing the US is doing is drawing a very deliberate legal distinction. They're blockading Iranian ports, not the strait itself. Freedom of navigation for ships going to non-Iranian destinations is theoretically preserved. That's a careful legal construction designed to avoid the charge that the US is closing an international waterway — which would be a much more aggressive legal posture.
And Iran is already calling it piracy.
Which is a direct challenge to that legal framing. Piracy has a specific meaning in international law — it's essentially unauthorized seizure or violence on the high seas for private ends. Iran is using the word rhetorically rather than technically, but the rhetorical move is effective because it frames the US as the lawless actor rather than the state conducting a legitimate belligerent operation.
So let's go back further in history, because the research here is genuinely fascinating. Where does this as a military tactic actually come from?
The modern concept traces to the late sixteenth century with the Dutch conducting blockade-like operations against Spanish ports in Flanders. By 1630, the Dutch had formally extended what had been land siege principles to sea warfare, claiming the right to confiscate neutral commerce bound for enemy ports. Then between 1674 and 1689, a series of treaties among the Dutch, English, French, and Swedes actually codified what a blockade meant — lawful exclusion of all commerce from an invested port or coastline.
So it started as basically a siege adapted for water.
That's the lineage. And the history of whether blockades actually work is genuinely mixed, which matters for thinking about what happens next. The clearest success case is the Union blockade of the Confederacy during the American Civil War. Over thirty-five hundred miles of coastline, initially very porous — Confederate blockade runners were getting through constantly in the early years. But it became progressively more effective and is considered a major factor in the Confederacy's economic collapse. The key word there is years. It took years.
What about the First World War? Because Britain's blockade of Germany is the one that always comes up in these conversations.
Britain's naval blockade of Germany in World War One was devastating — and it's the closest historical parallel to what the US is attempting with Iran economically. It cut off Germany from food and raw material imports to a degree that caused genuine civilian suffering, contributed to the breakdown of the German home front, and is seen as a significant factor in Germany's collapse in 1918. But again — four years. And Germany retaliated with submarine warfare that nearly strangled Britain in return. The US was partly drawn into the war because German U-boats were attacking neutral shipping, which connects directly to the question of what happens when you try to enforce a blockade against a determined adversary.
And then there's Japan in World War Two, which is the case where a blockade most decisively ended a war.
The US submarine and aerial mine campaign against Japan from 1941 to 1945 is probably the most effective blockade in modern history. It cut off Japan's oil and raw material imports, effectively strangled the Japanese war economy, and is considered a decisive factor in Japan's defeat. But — and this is critical — Japan is an island nation. There was no alternative route. The sea was the only way in or out. Iran is not an island.
Iran shares land borders with Iraq, Turkey, Afghanistan, Pakistan, and others. So a naval blockade of its ports is inherently less decisive than the Japanese case.
That's the fundamental strategic limitation. The bypass routes by sea are also limited — Saudi Aramco's East-West pipeline has capacity of about five million barrels per day, the UAE's Fujairah pipeline adds another one point five million, so you're looking at maybe three and a half million barrels per day of effective bypass capacity compared to the twenty-one million barrels per day that normally flows through the strait. But Iran's land borders mean it can still move goods and even oil in ways the blockade can't touch.
Let's talk about the Cuban Missile Crisis comparison for a second, because Kennedy's 1962 "quarantine" is the most direct precedent for this kind of naval pressure short of full war. And the outcome there was actually a negotiated climbdown.
The Cuban Missile Crisis is instructive but also misleading as a parallel. Kennedy's quarantine worked because the Soviets had a clear off-ramp — they turned their ships around, negotiations happened, the missiles came out of Cuba, and the US quietly removed Jupiter missiles from Turkey. The whole thing was resolved in thirteen days. But the reason it resolved in thirteen days is that neither side had actually fired a shot, and both sides had enormous incentive to avoid nuclear escalation. The pressure was entirely prospective — the threat of what might happen, not the reality of an ongoing war.
Whereas here, the US and Israel have been at war with Iran for forty-four days. Three thousand people are dead in Iran, over two thousand in Lebanon. This isn't prospective pressure — this is ongoing conflict with a blockade added on top.
Which changes the psychology entirely. Iran's military command has already called this piracy. The IRGC has said any military vessels approaching the strait will be, quote, dealt with severely. Two US destroyers transited the strait on Saturday to begin mine-clearing — that was the first US naval transit since the war began. The fact that it happened without incident is somewhat reassuring, but mine-clearing is a slow process and the strait is what US Navy officials have previously called an Iranian kill box.
Explain that term for people who haven't heard it.
The Strait of Hormuz is only twenty-one miles wide at its narrowest point, between Oman and Iran. Iran has spent decades building up coastal defense systems specifically designed to threaten ships in that confined space — anti-ship missiles, drone swarms, fast-attack boats, and mines. The idea is that any adversary trying to operate in the strait is operating within range of Iranian shore-based weapons throughout the entire transit. That's the kill box concept. It's not a new vulnerability — it's a deliberate Iranian strategic investment.
So when Admiral Stavridis says this is a big task and a big gamble, he's not being dramatic.
He's being precise. The blockade as described requires two aircraft carrier strike groups providing air cover, roughly a dozen destroyers and frigates operating outside the Persian Gulf, another six US warships plus UAE and Saudi navy vessels inside the Gulf. You're trying to bottle it up on both sides simultaneously. And the US has been building toward this — a Marine Expeditionary Unit with three warships and over two thousand Marines was deployed after the war started, and a second MEU plus a third carrier strike group are reportedly en route. So the hardware is either in place or arriving.
Here's the thing that strikes me about the strategic logic. Iran has essentially been running its own blockade of the strait — using missiles and drones to keep international shipping out while letting its own oil through and charging IRGC tolls on ships that wanted passage. The US blockade is designed to flip that completely. Now Iran's oil gets blocked while international shipping to non-Iranian ports is theoretically free.
Fortune described it as turning the tables on the Islamic Republic, and that framing is accurate. Iran weaponized the strait as its primary strategic tool in this conflict. The US is now attempting to take that weapon away while simultaneously weaponizing Iran's economic vulnerability. Iran's economy was already in freefall before the war even started. Food inflation hit one hundred and five percent annually by February. The rial lost sixty percent of its value after the June 2025 conflict with Israel, then dropped another eight percent on the black market since this war began. The regime issued its largest-ever currency denomination last month — a ten million rial note — a month after introducing the five million rial note. That's a classic sign of hyperinflationary spiral.
And Iran's oil revenue is basically the lifeline that keeps the regime functional.
About thirty billion dollars a year, with energy products accounting for roughly twenty-five percent of government revenue. Critically, the IRGC processes about fifty percent of Iran's oil exports and was collecting billions in tolls from strait traffic. If the blockade cuts that off, you're not just hurting the Iranian economy in the abstract — you're cutting off the IRGC's specific revenue stream. Robin Brooks at the Brookings Institution put it bluntly: the US can implode Iran's economy by shutting down its oil exports, and that might open the strait a lot faster than anything else.
He also made the interesting point that if the blockade is seen as ending the war quickly, oil prices might actually fall — because markets would price in a resolution. Which is sort of the optimistic scenario.
That's the bull case for this strategy. And it's not crazy — markets are forward-looking. Brent crude is up seven to eight percent this morning, sitting around a hundred and two to a hundred and three dollars per barrel. WTI is at a hundred and four dollars and twenty-four cents. But if the blockade creates a credible path to a deal, those prices could reverse. The problem is the credible path to a deal just collapsed in Islamabad.
Walk me through what happened in Islamabad, because that's the immediate trigger for all of this.
A fragile two-week ceasefire was brokered by Pakistan. It expires April 22nd — nine days from now. The Islamabad talks were meant to convert that ceasefire into a lasting deal. The US delegation was Vice President JD Vance, Jared Kushner, and Special Envoy Steve Witkoff. Iran's side was led by parliament speaker Mohammad Bagher Ghalibaf. The talks broke down over a single issue: the US demanded Iran commit to abandoning its nuclear weapons path. Iran refused, insisting on its right to a civilian nuclear program.
Which is... not a new impasse.
It's almost word-for-word the same sticking point that killed every version of the JCPOA negotiations going back years. The war has changed the military situation dramatically, but it has not changed Iran's fundamental position on nuclear sovereignty. And Trump's response to the collapse was characteristically direct: "We're sweeping the strait. Whether we make a deal or not makes no difference to me."
Which is either a brilliant negotiating posture or a genuine statement of intent. Probably both.
Probably both. The strategic logic is that Iran's economic pain is now so acute that the blockade will force concessions the diplomacy couldn't. An insider close to the Iranian establishment told Reuters that without sanctions relief, authorities will have trouble making payroll. That's not a minor detail — that's the regime being unable to pay its own security forces.
So let's get into the next twenty-four hours, because that's the other half of what Daniel is asking about. What do we actually expect?
The first question is whether there's a first incident. The two US destroyers that transited Saturday got through without engagement — but mine-clearing is a different operation from enforcing a blockade against a vessel trying to reach an Iranian port. The first real test will be when a ship that's bound for an Iranian port is intercepted and ordered to turn around, or when an Iranian vessel challenges a US warship in the strait.
And if that happens, the ceasefire that expires April 22nd is effectively dead.
In spirit it's already dead. The IRGC has said any military vessels approaching the strait will be considered a ceasefire violation. The US is sending military vessels into the strait. Those two positions are incompatible. The ceasefire is holding in the technical sense that there hasn't been a formal resumption of the strikes that characterized the first weeks of the war, but the blockade announcement has already blown through whatever political framework the ceasefire represented.
Ghalibaf's post on X went viral — two point nine million views — where he mocked Trump about gas prices. Quote: "Enjoy the current pump figures. With the so-called blockade, soon you'll be nostalgic for four to five dollar gas." That's not the rhetoric of a side looking for an off-ramp.
No, it's not. And it points to Trump's domestic vulnerability here. Oil at a hundred and four dollars a barrel means gas prices are heading sharply higher for American consumers. Trump built significant political capital on energy prices. If the blockade pushes prices to levels that create serious domestic backlash — and there's no quick resolution — that's a real political problem. The analyst Susannah Streeter at Wealth Club called this a hint of desperation, saying Trump has been cornered by Iran's defiance with hopes of an off-ramp replaced by fears of dangerous escalation.
I'd push back slightly on "desperation" — there's also a coherent strategic logic here that isn't desperate at all. If Iran's economy is genuinely on the edge of collapse, the blockade is a way to accelerate that collapse and force the nuclear concession. The question is whether Iran's leadership would rather make a deal or go down with the ship.
Dan Alamariu at Alpine Macro put it starkly: to survive, Iran's regime will need to either reform — which he argues it's incapable of — or export instability abroad. Absent that, it will likely fall, though the timing could be one to three years away. That's actually a sobering timeline if you're thinking about what the blockade is trying to accomplish. One to three years is not the same as twenty-four hours.
And the allied picture is pretty bleak for the US right now. The UK has explicitly refused to participate. Keir Starmer said the UK will not get dragged into the war, while simultaneously acknowledging that Iran's restrictions on Hormuz traffic are in breach of international law. Trump compared him to Neville Chamberlain.
France's Macron is organizing a meeting with the UK and other willing nations about a, quote, strictly defensive multinational mission to restore freedom of navigation — explicitly distancing from the warring parties. Which means Europe is trying to create a third option: not supporting Iran, not supporting the US blockade, but asserting that the strait should be open to everyone. That's a coherent legal position but it doesn't help the US diplomatically.
China is the wild card. China buys most of Iran's oil. If the blockade cuts off Iran's oil revenue, China loses a key supplier and faces higher global oil prices. The theory is that China will lean on Tehran to make a deal.
China denied reports that it's considering selling shoulder-fired anti-air missiles to Iran. Trump said he doubted China would arm Iran but warned of a fifty percent tariff if they did. And Trump is scheduled to visit China in mid-May — so there's an active diplomatic track there that creates some incentive for China to be cooperative. But China's interests aren't neatly aligned with the US position. They want cheap Iranian oil and they want regional stability, but they also don't want to be seen as a US proxy pressuring a partner.
So the scenario where China leans on Iran hard enough to produce a deal in the next forty-eight hours seems... optimistic.
Very optimistic. The more realistic near-term scenarios are: one, a tense standoff where the blockade is technically in place but no first contact occurs in the next twenty-four hours, and both sides wait to see who blinks; two, an incident in the strait — a drone, a mine, a fast-attack boat — that triggers escalation and effectively ends the ceasefire; or three, Iran makes some kind of limited symbolic concession that gives Trump a face-saving off-ramp without actually resolving the nuclear question.
Option three seems unlikely given that Ghalibaf just went on X to taunt Trump about gas prices.
That's not the behavior of a side preparing to offer concessions. But Iran's public posture and its back-channel behavior can be different things. The Islamabad talks happened at all — that's evidence of some Iranian willingness to negotiate even in the middle of a war.
What's your read on the mine threat specifically? Because the two destroyers transiting Saturday to begin mine-clearing — that feels like the most immediately dangerous element here.
Mines are the great equalizer in confined-water naval warfare. They're cheap, they're hard to detect, they're politically deniable — Iran can always claim it didn't place a particular mine. The US has the most sophisticated mine-countermeasures capability in the world, but mine-clearing in a contested environment is slow, dangerous work. If Iran has seeded the strait with mines since the war started, clearing a safe channel takes days to weeks, not hours. And Iran can replace mines faster than the US can clear them. This is one of the reasons former naval commanders have consistently warned that the strait is not a place you want to be operating a surface fleet in a conflict with Iran.
Let me bring up the historical effectiveness question again, because I think it's underappreciated. Every successful blockade in history that actually compelled an adversary to change behavior took years, not weeks. The Confederacy, Germany in World War One, Japan in World War Two — the timelines were measured in years. Is there any historical precedent for a naval blockade producing a quick political concession?
The Cuban Missile Crisis is the only case that comes close, and as we discussed, that was a quarantine that never actually stopped a ship — it was purely a threat that created space for negotiation. The other case people sometimes point to is the 1994 Haiti situation, where the US naval blockade contributed to the restoration of Aristide's government relatively quickly. But Haiti had no capacity to retaliate, no oil exports to protect, and no nuclear program. The comparison to Iran is essentially zero.
So the honest assessment is that if the goal is a quick resolution — days or weeks — the historical precedents don't support optimism. If the goal is a slow economic strangulation over months, the precedents are better, but the domestic political costs accumulate over that same period.
That's the core tension. And there's a second-order effect worth thinking about: what does this do to the global oil market structure over the medium term? If twenty-one million barrels per day of flow through the strait is disrupted even partially, the countries most affected are China, India, Japan, and South Korea — they account for sixty-seven percent of all Hormuz crude flows. Asian markets have far less flexibility than US markets, which have been less dependent on Gulf oil as domestic production rose. The US imported about zero point seven million barrels per day from the Persian Gulf through the strait in recent years — eleven percent of crude imports. That's significant but manageable. For Japan and South Korea, who have almost no domestic production, a prolonged disruption is a genuine crisis.
Which creates an interesting diplomatic dynamic where the countries most economically harmed by a prolonged blockade are US allies in Asia — Japan and South Korea — and the strategic competitor China.
And that creates pressure on all of them to push for a resolution, but through different channels. Japan and South Korea will be on the phone with Washington asking for assurances about non-Iranian port traffic. China will be managing its own Iran relationship while trying to avoid being caught in the middle of a US-Iran confrontation it didn't want.
One thing that hasn't come up yet that I want to flag: Iran's threat about no port in the Persian Gulf and the Sea of Oman remaining safe. That's not just about the strait. That's a threat against the UAE, Saudi Arabia, Bahrain — the Gulf Arab states. Those states have been providing some naval cooperation with the US. Saudi and UAE navy vessels are reportedly part of the blockade enforcement posture.
That threat is significant because it expands the potential conflict zone beyond the strait itself. Iran has previously demonstrated the ability to strike targets throughout the Gulf — the 2019 attacks on Saudi Aramco's Abqaiq and Khurais facilities showed what Iranian missiles and drones can do to Gulf Arab infrastructure. If Iran follows through on that threat in response to the blockade, you're looking at a regional war that goes well beyond the US-Iran bilateral conflict.
And Israel announced new ground operations in the Bint Jbeil area of southern Lebanon this morning. So the conflict is already multi-front.
Lebanon is where the death toll has been highest after Iran — over two thousand dead. The war started February 28th, and it's been a combination of Israeli and US strikes on Iran directly and Israeli operations in Lebanon. The Bint Jbeil operations suggest the Lebanon front hasn't quieted even during the ceasefire period.
Alright, let's talk about what the next twenty-four hours actually look like in terms of what to watch for. If you're following this story, what are the key indicators?
First and most immediately: does any vessel bound for an Iranian port attempt to transit and get stopped? That's the first real test of whether the blockade is effective in the sense the Declaration of Paris requires. Second: does Iran conduct any offensive action against US naval vessels, Gulf Arab ports, or other targets in response? Third: does China make any move — either diplomatic, in terms of leaning on Iran, or provocative, in terms of any military signaling? Fourth: the ceasefire technically expires April 22nd — watch for any formal announcement from Pakistan, Iran, or the US about whether that deadline is being extended or abandoned.
And the oil price is going to be a real-time sentiment indicator for all of this. A hundred and four dollar WTI this morning — if that number starts moving significantly higher, markets are pricing in escalation. If it stabilizes or starts pulling back, markets are pricing in some kind of resolution pathway.
Robin Brooks' point about prices falling if the blockade is seen as ending the war quickly is worth holding onto as a benchmark. If you see oil prices actually drop despite the blockade announcement, that's a signal that sophisticated market participants think this ends fast. If prices keep climbing, they're pricing in prolonged disruption.
What's your overall assessment? Honest read.
The strategic logic of the blockade is coherent — Iran's economy is genuinely fragile, oil revenue is the regime's lifeline, and cutting it off creates maximum pressure at minimum US military cost compared to ground operations. But the execution risks are severe. The strait is a confined space with Iranian defensive systems designed specifically for this scenario. The ceasefire is effectively over in spirit. Allied support is essentially absent. Iran's public posture is defiant rather than conciliatory. And the historical record on blockades producing quick results is poor. My read is that the next twenty-four hours are more likely to produce a dangerous incident than a diplomatic breakthrough — and that the US is betting on Iran's economic fragility to eventually force concessions that forty-four days of war and twenty-one hours of talks in Islamabad couldn't produce.
The Ghalibaf gas price taunt is going to look either very prescient or very embarrassing in about a week. There's not a lot of middle ground here.
That's the nature of the moment. The ceasefire expires in nine days. The blockade starts today. Iran has threatened to make every port in the Gulf unsafe. The US has three carrier strike groups either in place or en route. This is not a situation that stays in stasis for long.
Alright. There's obviously a lot more to say, and this story is going to keep moving. Keep an eye on the oil price, watch for any first-contact reports from the strait, and track what China does over the next forty-eight hours — that might be the most important signal of where this goes.
And watch for any back-channel signals that don't make the front pages. The Islamabad talks happened because both sides were willing to show up. That willingness doesn't just disappear because the talks failed. The question is whether the blockade creates enough additional pressure to bring Iran back to the table with a different position on the nuclear question — or whether it hardens their resolve.
Big thanks to Modal for the GPU credits that keep this whole operation running. And thanks as always to our producer Hilbert Flumingtop.
This has been My Weird Prompts. Find us at myweirdprompts dot com for all the ways to subscribe.
Stay safe out there.
