In the long arc of financial history, the instruments of power shift quietly before they shift decisively. Over the past decade, China has restructured its foreign reserves away from US Treasury bonds and toward dollar cash held in state banks — a technical maneuver that has transformed an old vulnerability into a new weapon. As US borrowing costs reach generational highs and the Federal Reserve's credibility frays, Beijing now holds the rare ability to inflict financial pain on Washington without suffering equivalent harm to itself. The age of mutually assured financial destruction may be giv