The complexion of the European war changed dramatically in the spring of 1940, necessitating an American state-building response. German victories in Scandinavia and the Low Countries compelled President Roosevelt to make a decision that he had put off for many months. After reviewing his options, he returned to the concept of business–government cooperation, reviving the moribund National Defense Advisory Commission (NDAC) in order to spur industrial mobilization. NDAC's most important leadership posts went to corporate liberals, who again supplied their knowledge of production and distribution to the federal government. Under corporate liberal direction, contingency planning yielded to institutional experimentation, and the preparedness period reached a more active stage. National defense gradually improved, despite the intrinsic difficulties surrounding conversion from civilian production to defense production and the loud protests of isolationists and other groups.

The National Defense Advisory Commission, officially known as the Advisory Commission to the Council of National Defense, originated with the Army Appropriation Act of 1916. NDAC's purpose had been to give advice on a wide range of defense matters to the Council of National Defense (CND), a body made up of selected members of the president's cabinet. In practice, NDAC did the work and CND never amounted to much. After World War I ended, NDAC remained on the statute book but quickly passed into disuse.

A massive German offensive, which ended the “phony war” phase of World War II, forced NDAC's recall. On April 9, 1940, German troops landed in Denmark and Norway. Denmark fell in a single short day,Norway in just twenty-three days. On May 10, the second stage of the “blitzkrieg” commenced. Operating in tandem, the Luftwaffe and Wehrmacht hit the Netherlands, Belgium, and Luxembourg. In short order, these nations capitulated. Germany completed the rout by driving into France, forcing that country to surrender after only a little more than a month.

The decisive nature of German triumph prompted U.S. action. On May 26, while French and British forces in France were still reeling under heavy Nazi assault, Roosevelt informed Americans that he intended “calling on men now engaged in private industry to help … in carrying out” the defense program, and that the public would “hear more of this in a few days.” On May 28, 1940, the president resuscitated the National Defense Advisory Commission.