The Underwriters Closed Hormuz Before the Missiles Did

On July 20, 2026, sixteen ships passed through the Strait of Hormuz. The next day it was ten. Before the war began on February 28 the ordinary count ran above 130 a day, through a waterway that carries about a fifth of the world's seaborne oil and liquefied gas. Nobody declared a blockade. No navy mined the channel, no ministry issued a closure order, and the water is exactly as navigable as it was in January. What changed is that the additional premium for taking a ship through went from 1 to 3 percent of the hull's value in early summer to between 7.5 and 10 percent by July 22, and at that price most owners simply stopped asking.

This publication argued in July that the honest gauge of a Gulf crisis was tanker traffic and insurance rates rather than ceasefire rhetoric. That was half right. Past a certain level the insurance rate stops being a gauge of the crisis and becomes the mechanism of it, and the people setting it are not diplomats, generals or oil traders. They are underwriters with their own capital at stake, which is precisely why their number is worth more than most of the commentary attached to it.

1. Underwriters sell war cover in seven-day slices, priced off the whole ship

A standard marine hull policy does not cover war. It never has: the exclusion is the oldest fault line in the market, and the cover is bought back separately as hull war insurance. What a shipowner then negotiates for a specific voyage is an additional premium, quoted not as a dollar figure but as a percentage of the vessel's insured value, and held open for about seven days at a time. Enter a listed area, pay a slice of the entire ship. Come back next week and the slice may be different, or there may be no quote at all.

Liability sits in a different market again. Thirteen mutual clubs make up the International Group of P&I Clubs and between them insure roughly nine tenths of the world's ocean-going tonnage against the things a ship does to other people: pollution, wreck removal, crew, cargo claims. War is carved out of that pooled cover too and written back with its own limits, currently 500 million dollars per vessel and sub-limited to 125 million for trades tied to Russia, Ukraine and Belarus. A cargo of crude therefore floats on three separate promises, any one of which can be withdrawn in a week.

2. A private committee in London redraws the map, and the rates follow

The map those promises are priced from belongs to the Joint War Committee, a body of underwriters drawn from Lloyd's syndicates and the company market. It publishes a list of areas considered to carry heightened war, strikes, terrorism and related perils. In late July it pushed the northern boundary of its Red Sea zone further up the sea. That is the whole action: a line moves on a chart.

The committee cannot stop a single vessel from sailing anywhere. What listing does is oblige an owner to notify underwriters before entering, which starts a negotiation over additional premium, which starts an argument with the charterer about who pays it, which ends with a ship going somewhere else. A private committee with no enforcement powers has become the closest thing the world has to a live geopolitical risk index, and unlike the analysts who publish risk scores, its members lose their own money when the score is wrong.

"Sanctions need a state to enforce them. A war risk quote enforces itself, because no owner sails uninsured."

3. Marsh puts a Hormuz transit at 10 percent of the hull, from 1 percent in June

Marcus Baker, who runs marine, cargo and logistics at the broker Marsh, put the Gulf additional premium at 7.5 to 10 percent of hull value on July 22, against 1 to 3 percent a few weeks earlier. On a tanker insured for 100 million dollars that is seven and a half to ten million dollars for one passage, and brokers were reporting Gulf premiums in double-digit millions per trip. In a calm year the same transit cost a fraction of a percent. The International Maritime Organization counted eight ships hit between July 13 and 20, which is what the quote is responding to, and the traffic count halved within days of the repricing.

The most revealing number in the market is not the Hormuz one. Vessels transiting Bab al-Mandab were paying about 0.5 percent of hull value in late July, up from 0.3 percent before the Houthis announced a maritime embargo on Saudi shipping on July 20. Ships calling at Saudi Arabia's west coast ports without going through the strait were paying 0.1 percent. Same country, same cargo, same week, five times the price for using the wrong door. Insurance does not price destinations. It prices the geography a ship has to survive to get there, which is the whole argument of our piece on chokepoints expressed as a rate rather than a map.

4. Iraq hit 283 ships, Iran 168, and the US Navy ended up working for Lloyd's

None of this is new, and the last full run of the experiment ended with warships. Across the Iran-Iraq war of 1980 to 1988, Iraq attacked 283 vessels and Iran 168, war risk rates in the Gulf settled around 5 percent, and by 1987 some operators could not buy cover at any price. Claims from the period ran to roughly two billion dollars, about half of it landing on Lloyd's.

Kuwait's answer to an uninsurable trade was not to pay more. It was to ask Washington for a flag. Eleven Kuwaiti tankers were reflagged as American ships so that the US Navy could legally escort them, and Operation Earnest Will ran from July 1987 to September 1988 as the largest naval convoy operation since 1945. Strip away the strategy and it was an insurance product with a destroyer attached: the state supplying, at public expense, the cover the private market had stopped selling. Which is the pattern worth holding onto. Underwriters withdraw first, navies arrive second, and the taxpayer pays a premium that never appears in anyone's marine budget.

5. Brokers count $3 billion of capacity, and underwriters will not quote it

Here is what makes the current pricing strange. Baker estimated global hull capacity at 2.5 to 3 billion dollars, and observed that since most vessels going through Hormuz are worth under 100 million, the cover could theoretically be placed twenty-five times over. War risk has historically been a profitable line. And yet underwriters have grown reluctant to offer spot terms at all. Capacity and appetite are different things, and the reason is structural: war losses are total losses. A hull that gets hit does not depreciate, it disappears, so the underwriter who misjudges a week does not book a bad quarter, he books the ship.

The other response to an unaffordable premium is to leave the system. Since the price cap on Russian crude made access to Western insurance the enforcement point, a parallel fleet has been assembled to operate without it: fewer than 100 vessels in February 2022, 343 by March 2025 on Brookings' count, growing at roughly seven ships a month, most of them probably without adequate spill liability cover. That was the design flaw in using insurance as a sanctions instrument, a point the sanctions report made about payments and which applies just as well at sea. If the leverage is that everyone needs the London market, the counter-strategy is to stop needing it, and several hundred elderly tankers now demonstrate that this is possible.

What the premium knows that the oil price does not

A barrel of Brent prices a dozen things at once: OPEC spare capacity, Chinese demand, the dollar, inventories, whatever the market believes about next month's diplomacy. That is why oil can rise 5 percent on missiles striking tankers and be read, reasonably, as a market that has decided the war stays contained. A war risk quote is narrower and therefore cleaner. It answers one question, for one ship, over the next seven days: what are the odds this hull is destroyed, and what do I need to be paid to carry them.

Nobody publishes that as an index, and it moves before the freight rates, before the diplomatic statements, and long before anything shows up in an inflation print. It is the most honest opinion available on the state of a conflict, held by people who have to mark themselves to market and who cannot hedge with a footnote. So when the underwriters move their number by a factor of five in a matter of weeks while the oil market holds its nerve, one of those two groups is looking at a different war. Which of them would you rather be short?