During the early stages of the Second World War, Wallis performed extensive studies of the German war economy and industry, concluding that with the selective destruction of strategic infrastructure targets, the German capacity to produce armaments could be reduced. Wallis believed that a fundamental means to ending the war would be to send bombing missions against German power sources and that the destruction of facilities such as coal mines, oil depots, hydroelectric dams and water supplies would leave Germany without a functional war industry and therefore having no ability to wage war.