Nearly a hundred billion dollars in intervention can only buy a week of respite? The results of the joint intervention by the U.S. and Japan have shrunk by nearly half, with the yen again approaching the 160 mark.

As global forex traders focus on the yen approaching the end of this week's trading, nearly half of the gains spurred by joint currency market interventions from the U.S. and Japanese governments have been retraced. This has led forex market traders to speculate that at least Japanese authorities may intervene again. During Friday's Asian trading session, the USD/JPY exchange rate was trading around 158.45, significantly distancing itself from the strong level of 155.23 reached on Monday. Last week, just before the first joint yen-buying action by Japan and the U.S. since 1998, the yen had neared 164 against the dollar, hovering close to a forty-year low. This sharp pullback underscores the limitations of currency market interventions in reversing the yen's long-term downward trend. The considerable interest rate differential between Japan and the U.S., Japan's high debt burden, and the uncertainty created by geopolitical issues in the Middle East that have driven up energy prices continue to weigh on the yen. Meanwhile, with rising oil prices and heightened expectations of tightening U.S. monetary policy, the dollar index recorded its largest single-day gain in two weeks on Thursday, reflecting waning optimism in the market that tensions in the Middle East would ease. Officials from the U.S. and Japanese governments have previously warned investors that they are determined to defend the yen if necessary. The current round of yen interventions is characterized by U.S. leadership and Japan-U.S. coordination because the issue has evolved from merely "Japan stabilizing its currency" to concerns about the dollar system and global financial stability: if Japan were to buy yen on a large scale independently, it would typically need to sell its extensive dollar assets, especially U.S. Treasury bonds, to raise dollars, potentially driving up U.S. Treasury yields and tightening U.S. financial conditions. Furthermore, extreme yen depreciation coupled with large yen carry trades may trigger a deleveraging in global equity markets and other risk assets if there is a sudden reversal. Direct coordination or even participation by the U.S. Treasury in these interventions can leverage the credibility of the issuer of the dollar and core participants in the global forex market, creating a stronger "policy signal effect" while reducing the pressure on Japan to sell off U.S. Treasury bonds. In other words, U.S. actions are not solely aimed at supporting the yen but are also about preventing a potential yen crisis from adversely affecting the U.S. financial markets through U.S. bonds, carry trades, and global liquidity. A significant $87 billion intervention fails to alter the fate determined by interest differentials; the yen quickly retraced its gains. Moh Siong Sim, a strategist at OCBC Bank, stated, Especially as the dollar-yen approaches the critical 160 level again, the likelihood of another intervention is high. However, he added that for the intervention to be truly effective, the Bank of Japan needs to accelerate interest rate hikes or there must be a macroeconomic turning point favorable to the Feds easing of monetary policy. Although the Bank of Japan kept its benchmark interest rate unchanged last week, overnight index swaps indicate a roughly 60% probability that the Bank of Japan will raise interest rates before September. Jun Mimura, a senior forex official, stated that authorities would coordinate responses to forex market volatility in conjunction with monetary policy. A week has passed since the initial round of intervention led to a sharp drop in the dollar-yen exchange rate, but the market focus has shifted back to U.S. Treasury yields, as they are seen as a catalyst for dollar strength. Forex traders also noted that the market has failed for the second time to push the dollar-yen below 155, which makes the intervention strategy led by U.S. Treasury Secretary Scott Bethent look more like a one-off action, commented Mark Cranfield, a Markets Live strategist at Bloomberg. The Japanese government stated that during the spring Golden Week holiday, it intervened three times in the forex market to support the yen, exceeding the recent practice of two consecutive interventions, as an additional round was evidently aimed at maximally enhancing psychological pressure on yen speculators. Analysis by financial institutions based on Bank of Japan accounts shows that the relevant government authorities, coordinated by the U.S. Treasury, may have utilized approximately $34 billion to intervene in the forex market on July 31 to support the yen. One day prior, authorities under U.S. coordination might have injected $53 billion; if confirmed, this could become the largest single-day forex market intervention on record. Idanna Apio, a portfolio manager at First Eagle Investments, stated that intervention can buy enough time to form a more credible fiscal or monetary policy mix or to convey a stronger message of support for the currency to investors. She added, But I dont think success can be achieved through intervention alone. With U.S. Treasury Chairman Kevin Walsh's policy-making framework making it difficult for Wall Street strategists to ascertain the next steps, traders remained cautious ahead of Friday's non-farm payroll data release. The market's implied volatility for the dollar-yen over a certain period continually rose on Friday, encompassing both non-farm data and next week's inflation report. Chalu Chananar, chief investment strategist at Saxo Markets, noted, There is still a possibility of joint intervention. U.S. Treasury Secretary Scott Bethent's rhetoric of at all costs and the Treasury Department's instructions for Wall Street banks to remain prepared for future actions suggest that last Friday's intervention may not just be a one-time action. The true enemy of the yen is not speculators but the policy dilemma facing the Bank of Japan. The primary reason the yen cannot maintain a sustained appreciation is that currency market interventions only alter short-term supply and demand, whereas interest rate differentials influence daily position returns. The Federal Reserve's policy rate remains at 3.50% to 3.75%, while the Bank of Japan's rate is only 1%, creating a differential of approximately 250 to 275 basis points; investors can continue to borrow low-interest yen and hold dollar assets to earn positive carry yields. Japan and the U.S.'s joint buying pushed the dollar-yen from around 164 down to 155.20, but as of August 7, it had risen back to 158.45, indicating that the interventions forced short sellers to cover positions temporarily without eliminating the economic incentive to re-establish short positions. The market does not unanimously believe that the Bank of Japan will resume a rate-hiking policy until 2027a Reuters survey shows that most analysts still expect the central bank to raise rates back to 1.25% within the yearbut even a 25-basis-point hike would not fundamentally change the current interest differential structure. The deeper constraint lies in the fact that the Bank of Japan cannot raise rates quickly or significantly like typical high-inflation economies. The International Monetary Fund estimates that Japan's total government debt will still be around 203% of GDP in 2026, and the Bank of Japan holds a long-term, large-scale position in Japanese government bonds; if policy rates and bond yields rise too quickly, the government's interest burden, the market losses for banks and insurance institutions, and liquidity pressures in the bond market could all expand simultaneously. Therefore, Japan needs to suppress imported inflation and yen depreciation while maintaining the stability of its fiscal and financial systems, often leading to a pace of interest rate hikes lagging behind the degree of tightening needed by the exchange rate. Interventions can buy time for policy adjustments but cannot substitute for a credible policy mix that can consistently narrow the interest differential, stabilize fiscal expectations, and attract capital inflows. Additionally, rising oil prices and Middle Eastern risks are simultaneously bolstering demand for the dollar as a safe-haven asset while deteriorating the trade conditions for Japan, an energy-importing country; the resilience of the U.S. economy and high Treasury yields have also quickly shifted the focus from official interventions back to the returns on dollar assets. Thus, the yen's mid-term outlook is more likely to trigger interventions repeatedly in the 158-160 range rather than form a sustained one-sided appreciation. The likelihood of joint interventions near the critical 160 level will impose sudden tail risks of several hundred points for those shorting the yen; however, only if the Bank of Japan significantly speeds up interest rate hikes, the Fed shifts to easing, energy prices decline, or there is a large-scale capital repatriation to Japan, may the yen upgrade from a "policy-supported rebound" to genuine trend appreciation.