The first joint US-Japan yen intervention since 2011, in the data
USD/JPY touched 163.74 on July 30, then fell as far as 155.32 within three sessions after Japan and the United States intervened together — the first coordinated action on the yen in 15 years. The daily reference series never printed either extreme.
On August 3, Japanese Finance Minister Satsuki Katayama confirmed that Japan had bought yen in coordination with the US Treasury — the first joint US-Japan currency intervention since 2011, and this time to strengthen the yen rather than weaken it. USD/JPY moved from a four-decade yen low near 164 to as low as 155.32 within three trading sessions, before giving part of the move back. The episode is also a working example of what a once-a-day reference rate structurally cannot show: neither the 163.74 extreme nor the 155.32 rebound extreme appears anywhere in the daily fix series.
What happened, session by session
The yen entered the last week of July at its weakest in about four decades, near the 40-year low around 164 set earlier in the month. On Thursday July 30 our live feed recorded a session high of 163.74 — then the dollar gave up almost six yen within hours, bottoming near 158, as analysts suspected official Japanese yen-buying. On Friday July 31 the pair retraced to nearly 161 before renewed selling — later confirmed as coordinated operations — pushed it to end the week near 157.4. President Donald Trump announced the US role on Sunday, and on Monday August 3 Finance Minister Satsuki Katayama confirmed that Japan had intervened jointly with the United States. The yen strengthened as far as 155.32 that day — its strongest in roughly three months — before giving part of the move back to the 157-158 area over the following sessions.
US confirmation came from the top: announcing the action on Sunday, President Donald Trump said "They have a weakening yen, and they wanted a little bit of help." Treasury Secretary Scott Bessent confirmed Friday's coordinated operations and said the US "will not hesitate to participate in further joint intervention." Katayama told reporters Japan "will not hesitate conducting further coordinated intervention."
Why a joint operation is different
Japan intervened alone repeatedly in 2026 — ¥11.7349 trillion between April 28 and May 27 — and USD/JPY was back above 162 within weeks each time. A joint operation changes two things analysts consistently flagged as the weakness of solo intervention: the signal (both governments are now committed on the record, with the US Treasury's balance sheet implied) and the follow-through risk for anyone positioned against it. Whether that durably changes the trend is not something this article forecasts; the factual record so far is three sessions of yen strength and two governments stating readiness to repeat the operation.
The last coordinated US-Japan intervention was in March 2011, when G7 central banks acted together to *weaken* the yen after the Tohoku earthquake had driven it to record strength. A joint operation to *strengthen* the yen has no precedent in the floating-rate era more recent than the late 1990s.
What the daily fix series missed
Here is the ECB daily reference series for USD/JPY across the episode, pulled from our own historical range endpoint. Intraday levels quoted in this article are what exchangerate.dev's live indicative feed — sampled roughly every 60 seconds — recorded across the episode. Wire-reported prints can differ by around a tenth of a yen, and more in fast markets; the 60-second archive is internal, so the daily series below is the part you can reproduce:
The series is smooth because it cannot see inside a day. Thursday's fix printed 162.94 on a day the live feed recorded a 163.74 high and a 158.05 low — neither the extreme behind the "40-year low" headlines nor the roughly five-yen intraday collapse exists in any daily series. Friday's fix was set around 14:10 CET, before the intervention move completed: the fix says 160.235, the week ended near 157.44, a gap of roughly 2.8 yen after the fix was set. And Monday's fix of 156.68 never saw the 155.32 rebound extreme. An application storing one observation per day recorded a smooth three-day decline and missed every number the event will be remembered by.
This is the same source-choice lesson as the July 30 move past 163, at larger scale and in the opposite direction. Daily reference rates are the right input for end-of-day accounting and long historical series. They are the wrong input for a display, alert, or risk check that has to react during a session in which a G7 government is operating in the market. The live USD/JPY page carries source, market_session, and data_updated_at on every observation; how to read source and market_session explains how to tell a live trading-day observation from a daily reference value.
Two governments confirmed a joint yen operation, and USD/JPY moved from 163.74 to 155.32 across three sessions. The daily fix series contains neither number. During an intervention week, the series an application stores decides whether it recorded the event or its shadow.