Emancipation Proclamation, proclamation issued by Abraham Lincoln on January 1, 1863, during the American Civil War, declaring all "slaves within any State, or designated part of a State. ..therefore…in rebellion,…he will be then, henceforth, and forever free.” The States concerned were enumerated in the proclamation; specifically exempted were slaves in some parts of the South then held by Union armies. Lincoln's issuing of the Emancipation Proclamation marked a radical change in his policies; historians consider it one of the greatest state documents of the United States. After the outbreak of the Civil War, the issue of slavery was exacerbated by the escape to Union lines of large numbers of slaves who volunteered to fight for their freedom and that of their fellow slaves. Under these circumstances, strict enforcement of established policy would have required the return of fugitive slaves to their Confederate masters and would have alienated the staunchest supporters of the Union cause in the North and abroad. Abolitionists had long urged Lincoln to free all slaves, and public opinion seemed to support this view. Advertisement Lincoln moved slowly and cautiously, however; On March 13, 1862, the federal government prohibited all Union Army officers from returning fugitive slaves, thus effectively nullifying the fugitive slave laws. On April 10, at Lincoln's initiative, Congress declared that the federal government would compensate slave owners who freed their slaves. All slaves in the District of Columbia were freed in this way on April 16, 1862. On June 19, 1862, Congress passed a measure prohibiting slavery in the territories of the United States, thus defying the Supreme Court's decision in the Dred Scott case, which ruled that Congress had no power to regulate slavery in the territories. Finally, following the Union victory at the Battle of Antietam (September 17, 1862), Lincoln issued a preliminary proclamation on September 22, declaring his intention to issue another proclamation within 100 days, freeing the slaves in states then deemed rebellious. On January 1, 1863, he issued the Emancipation Proclamation, granting freedom to approximately 3,120,000 slaves. With the entry into force of the 13th amendment in the United States.