Japan spent a record ¥15.4 trillion in one month to defend the yen

Japanese authorities spent 15.39 trillion yen, about $96.5 billion, intervening in the foreign-exchange market between 30 July and 26 August. The Finance Ministry released the total on Friday. It is the largest sum Japan has recorded for a single intervention round.

The previous monthly high was 11.73 trillion yen, spent during yen-buying operations around Golden Week in late April and early May. Added together, the two 2026 rounds now exceed 27 trillion yen. That already tops the previous annual record of about 15 trillion yen set in 2024.

The ministry did not list the exact days inside the July-August window. Bank of Japan data from earlier this month suggest the 30 July operation alone may have reached 9.6 trillion yen. If that figure holds when the quarterly breakdown appears, probably in early November, it would beat the confirmed daily record of 6.3 trillion yen from 30 April.

Why the yen was at a 40-year low

On 23 July the dollar traded near 163.99 yen, the weakest Japanese currency since 1986. The gap between U.S. and Japanese interest rates remained wide. Oil prices stayed high after the West Asia conflict disrupted cargoes. Markets also priced in heavier government spending under Prime Minister Sanae Takaichi, which would add to an already large public debt stock.

A weak yen lifts exporters such as Toyota and Sony. It also raises the yen cost of imported fuel, food and parts. That mix is why the ministry, not the central bank acting alone, decides when to enter the market. The Bank of Japan executes the trades on the ministry’s instruction.

After the late-July buying, the yen jumped from about 163 per dollar to as strong as 155.20 by 3 August. It then settled near 159.50 from 10 August. On Friday it was around 159.6. The rebound stopped the slide. It did not restore the levels seen before this year’s two intervention waves.

Washington joined for the first time in 28 years

On 3 August, Finance Minister Satsuki Katayama and U.S. Treasury Secretary Scott Bessent said Japanese and American authorities had carried out a joint yen-buying, dollar-selling operation on 31 July in New York hours. It was their first coordinated move of that kind in about 28 years. South Korean officials said the Bank of Korea timed its own won-buying with Japan’s, to amplify the effect.

President Donald Trump later confirmed the joint action aboard Air Force One. He called it a signal of friendship with Japan and said it was good for the world economy. To show that Tokyo could keep intervening at this scale, Washington has pointed to a COVID-era Federal Reserve backstop available to major central banks.

The last time the United States and Japan intervened together in G7 company was 2011, and the direction was the opposite. Then they sold yen to stop it rising after the Tohoku earthquake. The 2026 operation is a yen-support programme run against a dollar that markets still treat as the higher-yield currency.

What the number does not settle

Intervention can change a price for days or weeks. It does not close the rate gap that produced the slide. Friday’s print tells traders that Tokyo is willing to spend tens of billions of dollars in a month. It does not tell them whether the next defence will come at 160, 163 or some other line.

The ministry still has yen it can sell and dollars it can buy. The stock is not infinite. Each large operation also draws political attention in Washington, where a cheaper yen is often read as an export subsidy. The joint July trade reduces that complaint for now. A third Japanese solo round later in the autumn would test the friendship language Trump used on the plane.

For households the relevant figure is not the 15.4 trillion yen headline. It is the import bill that rose while the dollar sat near 164, and the partial relief that arrived when it fell toward 155. The yen at 159.6 on Friday sits between those two points. That is the market’s present verdict on how much of the intervention has stuck.