MOMENTUM FOR ABOLITIONISM The arguments of Northern abolitionists gained ground as the war continued, in part because of the value of slaves to the South but also because Northerners were stunned at the lengths Southerners would fight for slavery.
The North was also interested in denying the South imports and other aid from foreign countries, especially from Great Britain. One way to do this was to declare that the war was a war to end slavery; Britain, having abolished slavery decades earlier, would have a difficult time helping a nation fighting to preserve slavery.
For these and other reasons, Frederick Douglass's vocal campaign to change the war to a fight against slavery was increasingly supported by prominent white Northerners. In the summer of 1862 Congress finally authorized Union troops to confiscate Southern property, including slaves, who could then be used in military-support roles.
Freed slaves still could not fight, but Congress hoped the act would give them an incentive to flee toward advancing Union troops. No longer hopeful of luring the South back into the Union, Congress also put an end to slavery in Washington, D.C., and banned slavery in the territories.
In September 1862 Lincoln issued a preliminary Emancipation Proclamation freeing slaves in the South (though not in Northern border states, where slavery was still protected by the Constitution). The Emancipation Proclamation also finally permitted Southern freedpeople and Northern blacks to enter the armed services. Not everyone was pleased with the proclamation.
Many whites still believed the war should be fought only to restore the Union, not to free slaves. Combined with Lincoln's controversial suspension of the writ of habeas corpus (by which accused criminals are brought before a court to determine whether their detention is lawful), mounting losses on the battlefield, and an unpopular military draft (beginning in 1863), the Emancipation Proclamation helped bring about minor and major ".