China's near-monopoly of rare earth refining and rare earth magnet production has long posed a risk for US and global supply chain security. This risk became reality earlier this year as China imposed export restrictions on some rare earth elements, which also extended downstream to some rare earth magnets. Chinese magnet exports consequently fell by 77% from March to May 2025, causing global disruption to rare earth magnet supply chains. Against this backdrop of critical supply chain security risks, big news broke last week that the US Department of Defence had become the largest shareholder in MP Materials, purchasing a 15% stake for $400 million. The Department of Defence also announced they would guarantee a minimum price floor of $110/kg for the next 10 years, unlocking $1 billion of private finance for the construction of a new magnet facility with 10,000 tons per annum capacity. In this Insight, we analyse where this investment leaves US rare earth magnet supply security.