Japan spent a record $98.7 billion to prop up the yen over the past month in a joint action with the U.S., marking the largest currency intervention in history. The operation, confirmed by data released Friday, began in late July with the backing of Treasury Secretary Scott Bessent and brought Japan's total intervention spending this year to around $170 billion. The yen had weakened to nearly 164 to the dollar, a 40-year low, before the intervention pushed it back to between 159 and 160.

However, the currency has since given up many of its initial gains, underscoring the limited impact of government efforts to influence financial markets. Analysts at Citi noted that yen weakness is difficult to correct because foreign investors sell yen to hedge currency risk when investing in Japan's booming stock market. The U.S. has also attempted to stem rising bond yields with similarly limited success.

A notepad seen at a July 31 cabinet meeting indicated Bessent had "buying $5 billion to $10 billion of yen" on his agenda, though the exact U.S. contribution remains undisclosed.