The yen rescue is not an act of friendship

THE AMERICAN president may prefer to call it a gesture of friendship. The reality is closer to mutual survival. Last week the United States intervened in the foreign-exchange market alongside Japan to arrest the yen's slide to its weakest level against the dollar since 1986. The Federal Reserve Bank of New York sold euros to buy yen on behalf of the American Treasury. It was the first coordinated US-Japanese currency intervention since 2011, and it was not done out of charity.

The dollar had been trading at nearly 164 yen in the days before the operation, sending energy-import inflation through the Japanese economy and rattling bond markets in ways that had already spilled over into US Treasuries. Mr Scott Bessent, the Treasury secretary, had made his anxiety public in January, blaming a rising Japanese bond yield for pushing up American borrowing costs. On a notepad photographed at a cabinet meeting at Camp David on July 31st, a task was neatly itemised: "Buy Japanese Yen $5-10 bil."

Japan did most of the heavy lifting. On July 30th the Japanese government and the Bank of Japan spent an estimated 8.45 trillion yen, or roughly $53 billion, on a single day-the largest one-day intervention Tokyo has ever recorded, according to Bloomberg's estimate comparing central-bank accounts with broker forecasts. The yen jumped over 3% in a matter of hours. The American contribution was smaller but symbolic. Together the two central authorities drove the yen to 157.40 by the end of the week, its strongest close since May. Japanese officials told Reuters that Finance Minister Satsuki Katayama would formally announce the joint operation on Monday, the first such coordination in 15 years.

The incentive structure is straightforward. A collapsing yen would force Japan into a corner. The Bank of Japan has raised rates only to 1%, well below the Federal Reserve's upper band of 3.75%, and the yield gap sustains relentless carry trades that short the yen. Further rate hikes risk a fiscal crisis: Japan's prime minister, Sanae Takaichi, wants to fund new spending and a consumption-tax cut without scaring bond markets further. But if Tokyo tries to defend the yen alone, it must sell foreign reserves, much of them in the form of American Treasuries. That prospect alarms Mr Bessent, whose overriding policy goal is to keep US borrowing costs low.

Thus the Americans are helping Japan save the yen not because they care about Japanese importers but because they care about American yields. The arrangement is, in effect, an implicit subsidy to Japan's foreign-exchange defence that keeps the US Treasury market from another assault.

It is tempting to dismiss the exercise as window dressing. Currency interventions have a poor long-run track record. Japan spent more than $70 billion in a wave of buying in April and May this year; the yen recovered, then gave it all back and kept going. On March 27th 2026, when the dollar broke above 160 yen, the old debates resumed. Markets are efficient in the end; no treasury can stand athwart a yield differential that reflects a 2.75-percentage-point gap in policy rates.

But interventions do have a short-run purpose. They flush crowded positions. A yen that touches 164 is one where speculators have piled on with confidence, assuming authorities have run out of bullets or political will. A sudden 3% jump in a single session forces margin calls and closes short books. The coordinated element matters more than the dollar volume: when both central banks signal they are in the market, the risk for a one-way trade shifts. Speculators think twice when the counterparty is two governments rather than one.

The trouble is that this buys time, not a solution. The yen's problems are monetary, fiscal and energy-driven. Japan's budget deficits are unsustainable over any horizon longer than the next election. Its interest rate stays at 1% because anything else would threaten the government's ability to roll over its debt. And high oil prices punish a country that imports almost all of its energy. None of these factors is solved by a $60 billion injection.

What follows from there is a choice for both governments. The Americans have an interest in seeing Japan raise rates further, because a higher Japanese policy rate narrows the yield gap that is doing the real damage. Mr Bessent wrote on social media after the intervention that the Bank of Japan had "shown a strong commitment to monetary and financial stability." In diplomatic language that is a polite request to hurry up. The BOJ governor, Kazuo Ueda, is expected to raise rates again in September, according to a MUFG Research forecast, and possibly once more in early 2027. Markets are pricing that in; the risk is that they will not come fast enough to change the underlying carry-trade incentive.

For Japan, the harder question is fiscal. Ms Takaichi's appetite for spending and tax cuts is precisely what keeps bond yields volatile and the yen under pressure. The government cannot simultaneously promise fiscal expansion and a strong currency. It must choose. The intervention may keep the market at bay for a few more months. It will not fix the incentive that is tearing the yen apart.

The broader lesson for the international monetary order is less reassuring. The dollar's dominance has long allowed the United States to run twin deficits with few immediate consequences. It has also made every other major currency vulnerable when Washington shifts course. The Louvre Accord of 1987, which last saw the G7 jointly manage currencies, was born from a recognition that exchange rates were no longer set by market forces alone but by the distribution of national savings. That is true again today. The difference is that no one has drafted a new accord to replace the old one. The ad hoc coordination between Washington and Tokyo is a stopgap, not a system. A wiser answer would be a framework that addresses the root cause: the structural imbalances in global savings and the way American fiscal policy is exported to the rest of the world through the dollar. Until then, the next currency crisis will not be prevented by friendship. It will merely be postponed.