"Sink-Float process". The need for innovation was due to the exhaustion of ore supplies at the Helen mine. The process, which had been established at Broken Hill Proprietary by Guillaume Daniel Delprat at the turn of the century because of a similar exhaustion, had been tried once or twice in the US but on ore quite different from that at the Victoria. No Canadian mines had developed this technique; no large-scale equipment was available for experimentation and so the pilot plant would be uncertain and expensive. The gamble was a success, and Dunn pioneered again. The Victoria mine was able for a time from 1945 to supplant the Helen mine, while the latter changed from an open-pit to, in 1949, an underground operation. During the Second World War, the company benefited from the huge demand for steel by the military; however, financial calls from his associates, who needed or wanted to liquidate positions as a result of the French collapse, bedeviled Dunn, who retained in the end his Algoma shares and nothing else. Even then, he mortgaged them to his stockbroker friends. The benefit from a subsidized price for sinter, granted at the corporate nadir of 1935 by the provincial government of Mitchell Hepburn, was cancelled in 1942 by the Conant government. At times Dunn's relationship with the federal government minister in charge of the war effort, C. D. Howe was difficult; Beaverbrook relates a story in which he had to calm Winston Churchill because Howe or Mackenzie King, in the dark days of October 1940, had shredded Dunn's reputation. Howe threatened Dunn on 26 October 1940 with effective expropriation under the War Measures Act and the National Resources Mobilization Act: the government might obtain control of "trading, exportation, importation, production and manufacture" works, and require him "to place [himself], [his] services and [his] property at the disposal of His Majesty in right of Canada, as may be deemed necessary or expedient for securing the public safety, the defence of Canada, the maintenance of public order, or the efficient prosecution of the war, or for maintaining supplies or services essential to the life of the community." A letter to Churchill from Beaverbrook, who at the time was in the former's Ministry, was enough to secure the person and property of Dunn, but his health suffered ill effects, as presently will be related. The week after Dunn had a major surgery,