meddling in military strategy proved counterproductive. His explicit orders that Vicksburg be held no matter what sabotaged the only feasible defense and led directly to the fall of the city in 1863. Abolition of slavery By 1862, most Northern leaders realized that the mainstay of Southern secession, slavery, had to be attacked head-on. All the border states rejected President Lincoln's proposal for compensated emancipation. However, by 1865 all had begun the abolition of slavery, except Kentucky and Delaware. The Emancipation Proclamation was an executive order issued by Lincoln on January 1, 1863. In a single stroke it changed the legal status, as recognized by the U.S. government, of 3 million slaves in designated areas of the Confederacy from "slave" to "free". It had the practical effect that as soon as a slave escaped the control of the Confederate government, by running away or through advances of federal troops, the slave became legally and actually free. Plantation owners, realizing that emancipation would destroy their economic system, sometimes moved their slaves as far as possible out of reach of the Union Army. By June 1865, the Union Army controlled all of the Confederacy and liberated all of the designated slaves. The owners were never compensated. Nor were the slaves themselves. Many of the freedmen remained on the same plantation, others crowded into refugee camps operated by the Freedmen's Bureau. The Bureau provided food, housing, clothing, medical care, church services, some schooling, legal support, and arranged for labor contracts. Historian Leon Litwack has noted, "Neither white nor black Southerners were unaffected by the physical and emotional demands of the war. Scarcities of food and clothing, for example, imposed hardships on both races." Conditions were worse for blacks. Late in the war and soon after large numbers of blacks moved away from the plantation. The Freedmen's Bureau refugee camps saw infectious disease such as smallpox reach epidemic proportions. Jim Downs states: Disease and sickness had more devastating and fatal effects on emancipated slaves than on soldiers, since ex-slaves often lacked the basic necessities to survive. Emancipation liberated bondspeople from slavery, but they often lacked clean clothing, adequate shelter, proper food, and access to medicine in their escape toward Union lines. Many free slaves died once they secured refuge behind union camps Railroads The Union had a 3–1 superiority in railroad mileage and (even more important) an overwhelming advantage in engineers and mechanics in the