How did the war affect the relationship between private corporations and the federal government?

If you are talking about the United States during World War I OR World War II, here is your answer.

The US federal government took over significant control of private corporations during wartime. The government forced many businesses to switch from their normal operations in order to produce goods for the war effort. For example, during World War II, companies like Ford switched from making cars to things like tanks and ammunition. This type of government intervention would ensure the US was completely prepared for the war.