World War I was accompanied by major changes in the steel industry. Total war produced higher profits but huge, short-term strains. There was a major expansion of capacity, and a shake-up in long-established methods. Equally importantly, it marked the first large-scale involvement of government in the industry, initiating and helping finance extensions, and in control. Associated with these changes were the beginnings, at least, of industry-wide planning. The wartime boom was a prelude to the disasters of the 1920s. That decade brought a falling away of government interest and commitment, before dire commercial necessities brought their reassertion.

After the first few months of war it became clear that Laird's and the other established armament firms would be unable to meet the needs of the times unless major changes were made. In spring 1915 munitions shortages at the front caused a crisis, the creation of the Ministry of Munitions and greater pressure on the companies. By midsummer the Sheffield, Penistone and Birkenhead works had been declared controlled establishments under the provisions of a Munitions of War Act, which had received royal assent on 2 July. That month Cammell's agreed to build and manage a ‘national factory’ to produce in its first phase 8,000 shells a week. The company chose and bought a site at Nottingham; the government provided the capital for construction of the plant. (In contrast to other firms Cammell's refused to take commission on either its erection or its management.) Experience there showed how suddenly armament requirements could change and that apparently unlimited investment funds could be made available under the urgencies of war.