160 yen to the dollar. Then, in a matter of minutes, 155.50.

Japan’s Ministry of Finance broke nearly two years of silence on April 30, stepping into the foreign-exchange market to buy yen and sell dollars in what officials had been telegraphing for hours as inevitable. The currency surged as much as 3% — its biggest intraday gain in almost two years — before giving back roughly a third of those gains by the end of trading. Economic officials in the US were notified ahead of the move, consistent with Group-of-Seven agreements to alert counterparts before acting, according to a person familiar with the matter.

Finance Minister Satsuki Katayama had spent the day telling anyone who would listen that she was about to act. “The time is approaching when we will have to take decisive action,” she told reporters, adding, with the casual menace of someone who knows exactly what comes next: “Make sure you don’t let your smartphones out of your sight, whether you’re out and about or on your days off.”

Top currency diplomat Atsushi Mimura was even more direct. “This is our final evacuation warning to markets,” he said.

By late New York trading, the yen had settled around 156.40. By Friday in Asia it drifted to 156.99 — still enough for its steepest weekly gain in more than two months, but far from the knockout blow Tokyo was hoping to land.

What Broke the Yen

The yen’s collapse was not a mystery. It was the product of three forces converging at once — none of which Japan’s government controls.

The first is oil. Brent crude surpassed $126 per barrel on April 30, the highest since Russia’s invasion of Ukraine in 2022, according to Bloomberg. The catalyst: the US-Israeli aerial bombardment of Iran that began in late February and the subsequent closure of the Strait of Hormuz, through which roughly a fifth of the world’s oil passes. Threats by Tehran of “long and painful strikes” on US positions if Washington renewed attacks kept prices elevated into May. Japan, which depends heavily on imported energy, feels every dollar of crude inflation directly in its trade balance and currency.

The second is interest rates. The Bank of Japan held its benchmark at 0.75% this week while the Federal Reserve held steady at its own considerably higher level. The gap between the two rates continues to punish the yen, rewarding investors who borrow cheaply in yen and invest in dollar-denominated assets — the carry trade that has been a one-way bet for much of the past two years. Some strategists noted that BOJ Governor Kazuo Ueda’s reluctance to signal a near-term rate hike added to the pressure, even though the decision to hold was reportedly split.

The third is fiscal anxiety. Prime Minister Sanae Takaichi took office promising heavier government investment to stoke growth, a stance investors read as fiscally dovish. The yield on Japan’s benchmark 10-year government bond hit 2.535% on April 30, the highest since June 1997, according to Japan Bond Trading Co. Higher yields mean higher borrowing costs for the world’s most indebted government, and that pressure feeds back into yen weakness.

The link between oil and the yen is tighter than it appears. Brent Donnelly, president of Spectra Markets, noted that the drop in oil following the yen’s rally may have reflected traders unwinding correlated positions across both markets. “If you’re playing for higher oil, you are probably short yen and when you are getting smoked on the yen side, you sell your oil futures,” he told Bloomberg.

Billions Spent, Questions Remaining

Japan has been here before. In 2024, authorities spent roughly $100 billion across multiple rounds of yen-buying intervention, according to Bloomberg — including a record single-day purchase on April 29, 2024, followed by another round on May 1, for a combined 9.79 trillion yen ($62.2 billion), and another 5.53 trillion yen ($36.8 billion) in July.

The pattern is consistent: intervene sharply, move the currency temporarily, then watch the structural pressures push it back down. Sebastian Boyd, a macro strategist at Bloomberg, described yen intervention as “a bit like fighting the wind. Authorities can move the currency sharply if they wish, but rate expectations will keep pushing the yen weaker against the dollar.”

Past intervention has had “only a temporary effect on the yen if the underlying fundamentals haven’t shifted,” wrote Kristina Clifton, senior currency strategist at Commonwealth Bank of Australia. “Continued yen depreciation may prompt several rounds of intervention, which in turn would cause larger two-way swings in USD/JPY.”

Shaun Osborne, head of currency strategy at Scotiabank, noted that the aggressive interventions in 2022 and 2024 did eventually produce significant corrections — but they required more than one round of yen purchases each time. This intervention may be the first of several.

The Structural Problem

The deeper question is whether any amount of intervention can hold against forces Japan cannot dictate.

Oil prices are set by a war Tokyo did not start and cannot end. US interest rates are set by a Federal Reserve focused on American inflation and employment data. The carry trade is a rational response to the yawning gap between Japanese and American policy rates — a gap that may narrow if the BOJ hikes in June, as it signaled this week, but will not close anytime soon.

“At a time when the economy was garnering momentum, now we have this oil price shock, which is a big deal for Japan, which is an oil importer,” Sophia Drossos, a strategist and economist at Point72 Asset Management, told Bloomberg Radio. “The currency weakness in this context is a lot more pernicious.”

Chris Turner, global head of markets at ING, pointed to the variable that could change the calculus: whether the US Treasury joins the fight. “Taking into account high energy prices and Japan running substantially negative real interest rates, plus the dollar being in demand, Tokyo cannot expect a sustained drop in dollar-yen,” Turner said. “The wild card, however, would be whether the US Treasury gets involved.”

The US has only intervened in currency markets three times since 1995, according to the Richmond Fed, most recently after the 2011 earthquake in Japan. There is no sign Washington is prepared to do so now. Treasury representatives did not respond to requests for comment.

Firefighting With Finite Ammunition

Japan burned roughly $100 billion defending the yen in 2024. At that pace, the math becomes uncomfortable fast. Each intervention that fails to shift the structural picture depletes reserves that cannot easily be replaced.

Markets are watching for the next move. Japan heads into Golden Week holidays — Monday through Wednesday — and Mimura pointedly reminded reporters that his office remains open. The ECB and BOJ both signaled this week that rate hikes could come as soon as June. If the BOJ delivers, the rate differential narrows slightly, giving the yen a foothold it does not currently have. “Combined with the Bank of Japan’s ‘hawkish hold,’ if the market starts to price in a rate hike at the next meeting in June, yen buying could gather momentum,” Sakura Koike, an analyst at Mitsubishi UFJ Bank, wrote in a note.

But a rate hike against the backdrop of $126 oil and a war in the Persian Gulf is a small thing. Japan is fighting the wind, and the wind is blowing from Tehran, Washington, and the Strait of Hormuz — none of which answer to Tokyo. Central banks around the world are now in a position they did not choose: firefighting crises born of geopolitics and commodity shocks, armed with reserves that have limits and policy tools designed for a different era.

Sources