''As the South was turning away from solidarity with Roosevelt on domestic issues, Roosevelt’s own attention was turning to the coming of World War II—and there, in Katznelson’s telling, the South was completely supportive, far more so than the rest of the country. The dominant strain in the Republican Party in those days was isolationist, and, as Katznelson reminds us, the northern, urban wing of the Democratic Party included many Italian-Americans, German-Americans, and Irish-Americans who were skeptical about the war.
The South has always had a more martial culture than the country as a whole. Still, it isn’t entirely clear why the South was so militantly anti-Nazi—Adolf Hitler was a big fan of Gone With the Wind, and many prominent Nazis assumed that many in the South would find their racial views sympathetic, but they didn’t. The crucial steps before the Pearl Harbor attack that made the United States as prepared for the war as it was—including large increases in military spending, military aid to Great Britain, and the establishment of a draft—would all have been impossible without the enthusiastic backing of southerners in Congress. In return, the South got some assurances that the militarization of the United States would proceed in ways that did not threaten Jim Crow, such as the maintenance of segregated army units.''
http://www.nybooks.com/articles/archives/2013/sep/26/new-deal-we-didnt-know/?pagination=false