"In my view, the Commerce Department's practice of including all war product in real GNP is valid for the analysis pursued in this article. Just as military personnel were considered usefully employed for computing the unemployment rate for the total labor force, government purchases of their services and of other war goods and services were product, and product that was necessary for preserving the nation, its institutions, and its social fabric in the face of an external threat."
Vernon, J.R. 1994. "World War II Fiscal Policies and the End of the Great Depression". The Journal of Economic History. 54(4) p. 854.