The alliance between the United States and South Korea faces one of its most consequential tests in seventy-two years. Some observers believe it may be nearing its breaking point, and there is growing concern in both capitals that the existing framework is no longer sufficient to meet the strategic demands of a far more dangerous world. If the alliance is to be placed on a steadier footing with the U.S. administration, it must be modernized and made fit for purpose for both sides―not only to deter threats on the Korean Peninsula but to uphold regional order and counter authoritarian aggression beyond it.