Issued after the Union victory at Antietam, this preliminary proclamation granted freedom to more than 3 million slaves in the South. The proclamation exempted the border states, which, though faithful to the Union, continued to harbor slaveholders.
In addition, it expanded the political focus of the Civil War to include not only the preservation of the Union, but also the abolition of slavery. This isolated the South from anti-slavery nations such as France and Great Britain, who had once been conciliatory toward the Rebel states.
The presidential order also led to the creation of Black military forces in the army and navy. Three years later in 1865 — just weeks before Lincoln’s assassination — the 13th Amendment abolishing slavery in the U.S. was passed