The onset of war is often accompanied by dramatic shifts in demand and supply to meet new military needs. The First World War did this for many of the countries involved, and in the case of Japan too, though not a principal belligerent, the economy was seriously affected. For the iron and steel industry, the dramatic increase in demand combined with a shortage of supply created considerable problems. This highlighted some of the inherent weaknesses in the structure of the industry, and its vulnerability, and, in turn, the necessity for these to be addressed became apparent. Despite this need being clear, it was the contentious third expansion plan of the government-owned Yawata Steel Works that precipitated change, culminating in the Iron and Steel Industry Promotion Law of 1917. The submission of Yawata’s construction plan sparked a series of private debates and missives by leading industrialists, while government launched an investigative committee to consider the long-term development of the industry and some of the issues that so piqued the private sector. As a result, the Promotion Law’s measures not only reflected the imperatives that characterized the industry but also, importantly, the issues that were the focus of the private-sector concerns.