 Stewart approached the project with gusto , remarking that he " wrote an adaptation from a novel that tells about the fascist mice who are nibbling away at our country while we 're busy fighting a good war " . Stewart believed Hollywood had punished him for years for his political views , and felt vindicated by the assignment , declaring that " here was my compensation for the sabotage of my radical attempt to do my bit ... " . The script was the proudest moment of his entire career . Stewart , however , had extensive problems adapting the novel for the screen , and filming — originally due to begin in June 1942 — was delayed for several months while he worked on the screenplay . He consulted with the Bureau of Motion Pictures in the U.S. Office of War Information , an agency of the federal government created in June 1942 to promote patriotism and warn the public about domestic spying . 
