According to an AP report on August 3, U.S. President Trump and Japanese Finance Minister Mayumi Kotobuki confirmed that both sides intervened in the foreign exchange market. The USD/JPY had previously risen above 163, with the yen nearing a 40-year low against the dollar, before retreating to around 156.34 in early Monday trading.
The current market question is straightforward: Is the yen's rebound a result of short-term squeezing from the joint intervention, or the beginning of a yen trend reversal?
The mechanism of foreign exchange intervention is not complex. Governments or central banks directly buy their own currency, using large amounts of funds to support the price. For investors, a sudden strengthening of the yen can also disrupt yen-funded trades. In recent years, the low-yielding yen has often been used to purchase higher-yielding assets. Once the yen rebounds, U.S. stocks, crypto assets, the U.S. dollar index, and the Japanese stock market may all be affected.
This intervention is garnering more attention because the U.S. has joined in. Since 2011, the U.S. and Japan have rarely acted together in this manner. The official narrative presented by Mayumi Kotobuki is that the joint action is aimed at curbing "excessive depreciation." Opposition politician Jun Ogawa has reportedly criticized that without structural adjustments, temporary interventions are unlikely to last more than a few days.
U.S. Participation Amplifies Short-Term Deterrence
The yen's rebound in this round first came from position adjustments. The USD/JPY had approached 163, and short yen trades were already crowded. After the signal of joint U.S.-Japan entry, bears would cover their short positions first, naturally driving the price lower swiftly.
The actual scale of yen purchases this time is still pending confirmation through official monthly data. Based on trader accounts and central bank account changes, the scale may reach several billion dollars. This magnitude is sufficient to alter the short-term pace but does not yet prove a trend reversal.
The signal from the U.S. Treasury also reinforces deterrence. According to a previous Reuters report, the U.S. Treasury informed several banks that they may need to prepare for future yen interventions. Other media reports indicated that on-site photos showed notes outlining a yen-buying plan. This is better understood as a policy stance rather than a fully executed official commitment.
The U.S. intervention has changed the risk calculation for traders. In the past, with Japan's unilateral intervention, the market would question how many more U.S. dollar assets Japan could sell and how long it could hold out. If the U.S. is willing to cooperate, the cost of quickly pushing the USD/JPY back to an extreme position would be higher.
However, intervention addresses the speed issue, not the direction issue. As long as U.S. interest rates remain significantly higher than Japan's, the logic of borrowing yen to buy U.S. dollar assets remains. The foreign exchange market will respect official buying, but will not give up carry trades solely because of one round of buying.
Bank of Japan Signal Determines Validity
For intervention to shift from a "one-off" to a sustained effort, the Bank of Japan's cooperation is needed. The Bank of Japan this time kept its uncollateralized overnight call rate target at around 1.0% unchanged, but signaled a hawkish bias post-meeting. Governor Kuroda's statement encourages the market to continue to hold onto expectations of future rate hikes.
The meaning of a hawkish signal is that although the central bank did not raise rates this time, it is willing to allow the market to price in future actions in advance. As long as investors believe that Japanese rates will continue to rise, the attractiveness of shorting the yen will decrease.
This is also key to whether the yen's rebound can be prolonged. If expectations of a rate hike in September continue to heat up, the market will tend to interpret this round of intervention as a coordinated action: the government first stabilizing exchange rate fluctuations, and the Bank of Japan then using interest rates to fill the fundamental gap. USD/JPY bulls will be more cautious, and yen funding trades may reduce leverage.
If the Bank of Japan only provides verbal hawkishness and actual rate hikes are further postponed, the market will quickly retest the official bottom line. In the past, Japan's interventions have often led to short-term rebounds, but the effects have quickly diminished when the interest rate differential has not significantly narrowed.
Former BOJ official Jun Ogawa's criticism of not being able to "hold out for more than a few days" precisely points to the validity period. The foreign exchange market is not afraid of the government intervening once; what they fear is if the policy framework truly changes. If the framework remains unchanged, intervention is more like a costly warning.
Tax Cut Agenda Undermines Long-Term Credibility
The issue with the yen also lies in fiscal policy. While the Japanese government aims to stabilize the exchange rate, domestic politics are pushing for tax cuts and fiscal support. Putting these two lines together raises doubts in the market about whether the policy objectives are aligned.
Tax cuts may improve short-term cash flows for residents and businesses, but if investors believe they will widen the deficit and increase debt issuance pressure, the yen may come under pressure instead. The market will question whether the Japanese government is tightening financial conditions to stabilize the yen or using fiscal expansion to support the economy.
In Jun Ogawa's criticism, the part that truly influences market pricing is when he links intervention with Prime Minister Koshi early tax cuts proposed by the ruling party. This points to the tug-of-war between fiscal policy and exchange rates: while the government can buy yen with foreign exchange reserves, if fiscal policy continues to send out loose signals, the forex market will doubt how long stability can be maintained.
For Japan, a weak yen is not simply a boost for exports. An excessively weak yen will raise import costs, squeeze household purchasing power, and make it harder to control inflation. The government needs to prevent a free fall in the currency's value while avoiding rapid rate hikes that could harm the economy and fiscal financing.
This joint US-Japan intervention was forceful, but it did not automatically resolve the underlying contradictions. It was more like shifting the market from a one-sided yen short position back to a posture of awaiting policy validation.
September Interest Rate and Fiscal Caliber Face Examination
Whether the US dollar can maintain its range against the yen post-intervention, the key variable is not how many yen have been purchased, but whether the Bank of Japan and the government can send a unified signal.
If the Bank of Japan continues to emphasize a rate hike path in September, possibly even taking concrete actions, the market may reinterpret this intervention as the starting point for a trend reversal. This pressure will not only affect USD/JPY long positions but also impact cross-asset trades relying on low-yielding yen funding.
If the rate hike falters and the tax cut agenda strengthens fiscal expansion expectations, a yen rebound is more likely to revert to a short squeeze phase. While US involvement can enhance short-term deterrence, it cannot resolve Japan's interest rate differential and fiscal credibility issues in the long run.
The US and Japan jointly buying yen indicates that the policy stance is firmer than what the market anticipated. For the yen to transition from a rebound to a reversal, it will require both the Bank of Japan and fiscal policy to provide a consistent answer.
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