The US Treasury Department just did something it hasn’t done in over a decade. On August 1, it stepped directly into foreign exchange markets, buying Japanese yen in a coordinated operation with Tokyo that marked the first American forex intervention since the G7’s 2011 effort to stabilize the yen after Japan’s earthquake and tsunami.

It was also the first time the US had bought yen since 1998.

What actually happened

Treasury Secretary Scott Bessent, the former hedge-fund manager, authorized the purchase of yen using an estimated $5-10 billion in funds. The money came from euro sales routed through the Federal Reserve’s FIMA facility, a mechanism that lets foreign central banks swap their holdings with the Fed.

Japan, for its part, went considerably bigger. Tokyo’s total yen purchases on the day reached approximately $36 billion, dwarfing the American contribution.

The trigger was the yen’s slide to a 40-year low against the dollar, approaching 164 yen per dollar.

Bessent justified the move by pointing to what he called “disorderly yen movements” driven by substantial undervaluation.

The immediate effect was measurable. The dollar dropped as much as 1% against the yen, falling to approximately 156.34. In the days that followed, the dollar fluctuated by as much as 5% against the Japanese currency.

Why analysts are raising eyebrows

Steven Englander, a strategist at Standard Chartered, described both the timing and the coordination as puzzling. His core objection was straightforward: the yen simply wasn’t a top US trade issue.

The structure of the intervention raised additional questions. This wasn’t a multilateral G7 action with broad international consensus. It was a bilateral operation between two allied nations.

Both the US and Japan signaled readiness for further interventions if conditions warranted.

What this means for markets and crypto investors

For traditional forex markets, the intervention creates a complicated dynamic. Traders who had been shorting the yen, a popular carry trade given Japan’s historically low interest rates, got a painful reminder that governments can and will move against consensus positioning. The 5% post-intervention fluctuation in the dollar-yen pair illustrates just how violently markets can react when policy surprises collide with crowded trades.

The more practical concern for crypto investors is the volatility transmission mechanism. Sharp moves in dollar-yen tend to ripple across all risk assets, including Bitcoin and major altcoins. The yen carry trade, where investors borrow cheaply in yen to fund purchases of higher-yielding assets, has historically been a significant source of liquidity for speculative markets. When that trade unwinds violently, as it did in August 2024, crypto markets tend to feel the impact.