Japan’s 10-year government bond yield hit 2.39 percent on April 3. The highest since February 1999. Twenty-seven years of near-zero rates ended because a strait 7,000 kilometres away closed and the oil that flows through it stopped arriving at Japanese refineries at a price the economy could absorb. The molecule that cannot pass through the Strait of Hormuz just broke the bond market that has anchored global finance for a generation.

Japan imports nearly all of its oil, roughly 90 percent from the Middle East through Hormuz. When the strait closed, physical Dubai crude rose from $73 to $140. Gasoline hit record highs. The Bank of Japan, which spent three decades at or below zero, now faces 60 to 71 percent odds of hiking at its April 27 meeting. Bond traders sold. The yield surged 27 basis points in a month. The number 2.39 is the sound of the last major central bank being forced off zero by an oil shock it did not start and cannot stop.

Here is why this matters beyond Tokyo. Japan holds approximately $1.1 trillion in US Treasuries, the largest foreign holder. When the BoJ raises rates, Japanese institutions earn more at home. The incentive to hold American bonds diminishes. If Japan repatriates capital, US borrowing costs rise at the moment the United States is proposing $1.5 trillion in defence spending funded by debt. The war drives the oil that drives Japanese inflation that drives the BoJ hike that pulls capital home from Treasuries that raises the cost of funding the war that drove the oil. The circle does not need to complete. It only needs to start. It started April 3.

The US Treasury bought back $15 billion of its own debt that same day. The largest buyback in history. If Japan’s appetite for American bonds weakens because BoJ is tightening, the US must absorb more of its own issuance. The Treasury becomes its own market-maker not because the market has failed but because the largest foreign buyer is being pulled away by the same oil shock that created the need for the debt.

The Fed is frozen at 3.50 to 3.75 percent. It cannot cut because oil-driven inflation is above target. The BoJ is hiking because the same oil-driven inflation has reached Tokyo. Two central banks on opposite sides of the Pacific, paralysed in opposite directions by the same molecule trapped in the same strait. The Fed cannot ease. The BoJ cannot hold. Both are hostage to the physical price of a barrel of crude that neither government controls and neither military can deliver.

WTI closed at $111.54, up 11.4 percent in a single week. Brent paper at $109. Dubai physical at $140. The screen says one number. The tanker says another. The Japanese bond market, which had not moved this far since the Asian Financial Crisis, says the tanker is right.

The molecule does not trade bonds. But the bonds fund the war that closed the strait that trapped the molecule that broke the yield curve that anchors the debt that funds the war.

Twenty-seven years of stability ended this week. The instrument that ended it was not a central bank. It was a 34-kilometre waterway and the molecule that can no longer pass through it.