Abstract: In this Article, I examine a phenomenon unfolding within the United States’s military legal establishment: an effort by a segment of military lawyers to define how the law of armed conflict (LOAC) applies to the wars they anticipate fighting in the future. I refer to this effort as LSCO lawyering: the development, advancement, and institutionalization of a vision of LOAC tailored to large-scale combat operations (LSCOs), understood here as multi-domain warfare against a peer adversary such as China. Drawing on doctrinal materials, planning documents, and conversations with current and former armed-forces legal advisers from the United States and allied or partner forces, I trace how LSCO lawyering reflects a diagnosis of interpretive and institutional crisis—a perceived mismatch between prevailing legal expectations and the operational realities of high-intensity war—and a response that aims not to dismantle LOAC but to reassert it on terms viewed as credible and feasible under conditions of existential conflict. At the heart of this project lies a reconfiguration of what I call American international humanitarian law (IHL): the United States’s distinctive assemblage of legal interpretations, operational practices, and normative commitments that shape its approach to the conduct of hostilities. While LSCO lawyering is often framed internally as a modest clarification of existing law, I suggest that it functions as a far-reaching attempt to reshape the interpretive ecosystem within which LOAC is applied by privileging internal coherence, institutional discretion, and operational speed over policy overlays, external scrutiny, and extensive civilian-protection norms. The LSCO lawyering project does not reject the law, but it does aim to narrow its aperture to ensure that legal interpretation does not require, in the view of its proponents, normatively undue or operationally unsustainable limits on commanders preparing to fight—violent, vicious, and fast—in a potentially existential war, which would entail extraordinarily high consequences for civilian death and destruction. The emergence of LSCO lawyering sheds light on deeper conditions within the law of armed conflict’s normative and interpretive architecture. It brings to the surface long-standing tensions—between operational feasibility and civilian protection, between internal judgment and external review, between doctrinal minimalism and progressive development—that have shaped the field for decades. As a project grounded in anticipatory planning, LSCO lawyering highlights the degree to which LOAC interpretation is shaped not only by treaty text or customary practice but also by institutional culture, professional memory, and perceived strategic necessity. In that sense, it offers a revealing case through which to examine the evolving contours of LOAC as a legal, operational, and epistemic system—one whose boundaries are still being contested and whose authority remains under active construction.