Japan spent a record $96.5 billion in a month to support the yen

Japan spent 15.4 trillion yen, roughly $96.5 billion, intervening in currency markets between July 30 and August 26, according to Finance Ministry data reported by Reuters. The amount shows how aggressively Tokyo has tried to resist a slide in the yen near levels not seen in decades.

Currency intervention is simple in concept. The government sells foreign currency, usually dollars, and buys yen. That creates demand for the domestic currency and can slow or reverse a rapid fall.

The harder question is whether intervention can change the forces driving the exchange rate in the first place.

The yen has been under pressure because interest rates in Japan have remained relatively low compared with those in the United States and other major economies. Investors can earn higher returns by holding assets denominated in higher-yielding currencies, which reduces demand for yen.

That gap also encourages carry trades, where investors borrow in a low-interest-rate currency and invest elsewhere. As long as the interest-rate difference remains wide and markets are calm, the trade can reinforce weakness in the funding currency.

Japan’s problem is that a weaker yen has both benefits and costs. Exporters can become more competitive abroad and overseas earnings are worth more when converted back into yen. But households and businesses pay more for imported fuel, food and raw materials.

For an economy that imports much of its energy, those costs can become politically sensitive. A weak currency can raise inflation even when domestic demand is not especially strong.

That is why the scale of the intervention matters. Nearly $100 billion in a month signals that authorities are willing to spend heavily to prevent disorderly moves. It can also make traders more cautious about betting aggressively against the yen because another official operation could arrive without warning.

Still, intervention works best when it is aligned with broader monetary and economic conditions. If the interest-rate gap remains large, market pressure can return after the immediate impact fades.

The Bank of Japan therefore sits at the centre of the longer-term story. Any shift in Japanese interest rates, inflation expectations or policy guidance can have a more durable effect on the yen than repeated market operations alone.

Tokyo has shown it is prepared to defend the currency. The next question is whether the economic forces pushing the yen lower begin to change, or whether the government has to keep paying to hold the line.