"The Arsenal of Democracy" was a slogan coined by President Franklin D. Roosevelt in Dec. 1940 promising to help the British and French fight the Germans by giving them military supplies while staying out of the actual fighting.
He had to do that because the isolationist movement was very strong, Poland, Belgium, Netherlands, Britain, Norway, Denmark, and France, amoung others were losing to the Nazis and asking for help. Russia was not attack by Nazis until June 1941.
The isolationists wanted the US to stay out of the war in Europe, they felt it would never affect the USA. Of course, the Nazi ally, Japan, fixed that in December 1941.
