On August 3, Japanese Finance Minister Katsunobu Kato and U.S. Treasury Secretary Scott Bessent publicly confirmed that both monetary authorities executed a coordinated intervention on July 31, purchasing yen to shore up its value. In this operation, Japan injected a single-day total of 8.45 trillion yen (approximately $52.8 billion), while the U.S. entered the market through the New York Fed by selling euros to buy yen, with an estimated scale ranging between $5 billion and $10 billion.

Prior to the intervention, the yen had been on a persistent weakening streak, with the dollar-yen pair touching 163.98 at one point, marking the lowest level for the Japanese currency since 1986.

Why Washington stepped in

From a strategic standpoint, the primary motivation behind U.S. participation in this intervention is to safeguard the stability of its own Treasury bond market. Japan stands as the largest overseas holder of U.S. Treasuries. Should the yen continue its depreciation spiral, Tokyo would be compelled to liquidate substantial amounts of American debt to secure dollars for market operations. Such massive selling would drive up Treasury yields and intensify the interest burden on U.S. government debt. With federal debt already surpassing the $40 trillion threshold and annual interest payments exceeding $1 trillion, any upward movement in rates would further aggravate Washington's fiscal strain.

Why the yen's weakness persists

However, the coordinated intervention may do little to reverse the yen's structural downtrend, as the root cause lies in the persistent interest rate differential between the two economies. Japan's expansionary fiscal policies, including economic stimulus packages and living-cost subsidies, have continuously ballooned its public debt load. With government debt exceeding 240% of GDP, Tokyo can ill afford the additional debt-servicing costs that higher rates would entail. Constrained by this fiscal reality, the Bank of Japan's tightening cycle, which began in March 2024, has remained notably gradual, failing to narrow the gap against the Fed's elevated policy rate at any meaningful pace.

Meanwhile, the sustained rate differential continues to fuel yen carry-trade activity. Investors borrow the low-yielding yen, convert it into dollars, and allocate the proceeds to higher-yielding assets, thereby generating persistent structural selling pressure on the Japanese currency in the foreign exchange market.