For the first time in 28 years, the US government is spending money to prop up another country's currency — a move that raises eyebrows for American taxpayers but aims to steady a key ally.

• The US Treasury is stepping in to support Japan's yen, which has been weakening.
• A leaked handwritten note from Treasury Secretary Scott Bessent read "buy Japanese yen, 5 to 10 billion."
• One theory is that the US is genuinely buying yen to shore it up because of its close ties to Japan.
• Another theory is the note was leaked on purpose — letting every trader see it could scare markets into pushing the yen back up without spending much.

Outlook: Traders will watch to see whether the US actually buys yen or was just bluffing to move the market.