South Korean won jumps 2% after rare dollar-selling intervention

South Korea's won strengthened sharply after market participants said the country's foreign-exchange authorities joined a rare coordinated intervention with Japan, with U.S. support seen through a rate check that helped amplify pressure on the dollar. The won climbed about 2% to around 1,418 per dollar, reaching its strongest level since Oct. 16, 2025, while the yen jumped more than 3% intraday to roughly 157.8 per dollar, its best single-day performance in nearly two years. The intervention took place during New York trading hours, when dollar liquidity is deepest, and was viewed by traders as a deliberate effort to maximize market impact. South Korea and Japan sold dollars during the same trading window, while U.S. monetary authorities were seen signaling support through a rate check, though it remains unclear whether Washington directly sold dollars. The last time Japan and South Korea jointly stepped into currency markets was in 2011 after the Tohoku earthquake. The move came with the yen under heavy pressure after trading near 40-year lows, and after Japan had already spent more than $73 billion earlier in 2026 defending its currency. On July 31, the Bank of Japan kept its interest rate unchanged at 1% but signaled that further rate hikes remain possible because of persistent inflationary pressures. Analysts said the durability of the won and yen rebound may depend less on one-off intervention than on whether Japanese policymakers follow through with tighter policy. The currency shift also matters for wider risk markets because a stronger yen can pressure yen-funded carry trades, in which investors borrow cheaply in Japan and deploy capital into higher-yielding assets elsewhere. Bearish bets against the yen exceed $11.65 billion, and any forced unwinding could ripple through global assets, including crypto, even as the Nikkei and Kospi both posted gains after the intervention.