of dramatic change in the poor, heavily rural South as new industries and military bases were developed by the Federal government, providing badly needed capital and infrastructure in many regions. People from all parts of the US came to the South for military training and work in the region's many bases and new industries. During and after the war millions of hard-scrabble farmers, both white and black, left agriculture for urban jobs. The United States began mobilizing for war in a major way in the spring of 1940. The warm sunny weather of the South proved ideal for building 60 percent of the Army's new training camps and nearly half the new airfields, In all 40 percent of spending on new military installations went to the South. For example, sleepy Starke, Florida, a town of 1,500 people in 1940, became the base of Camp Blanding. By March 1941, 20,000 men were constructing a permanent camp for 60,000 soldiers. Money flowed freely for the war effort, as over $4 billion went into military facilities in the South, and another $5 billion into defense plants. Major shipyards were built in Virginia, Charleston, and along the Gulf Coast. Huge warplane plants were opened in Dallas-Fort Worth and Georgia. The most secret and expensive operation was at Oak Ridge, Tennessee, where unlimited amounts of locally generated electricity were used to prepare uranium for the atom bomb. The number of production workers doubled during the war. Most training centers, factories and shipyards were closed in 1945 and the families that left hardscrabble farms often remained to find jobs in the urban South. The region had finally reached the take off stage into industrial and commercial growth, although its income and wage levels lagged well behind the national average. Nevertheless, as George B. Tindall notes, the transformation was, "The demonstration of industrial potential, new habits of mind, and a recognition that industrialization demanded community services." Civilian support for war effort Early in the war, it became apparent that German U-boats were using the backlighting of coastal cities in the Eastern Seaboard and the South to destroy ships exiting harbors. It became the first duty of civilians recruited for the local civilian defense to ensure that lights were either off or thick curtains drawn over all windows at night. State Guards were reformed for internal security duties to replace the National Guardsmen who were federalized and sent