The United States maintained its Constitutional Republic government structure throughout World War II.
Certain expediencies were taken within the existing structure of the Federal government, such as conscription and other violations of civil liberties, including the internment and later dispersal of Japanese-Americans.
The United States entered World War II with the Administration that had been at the helm of the nation since 1932, that of Franklin Delano Roosevelt.
Roosevelt sought and won an unprecedented fourth term in office in 1944, but this time with Harry S. Truman as his Vice President.
Roosevelt, who had been a victim of Guillain-Barré Syndrome early in life, died in April 1945, and Truman assumed the Presidency through the end of the war.