From Ohio History Central
For the first two years of the war, Lincoln struggled to find effective military leaders. Generals such as George McClellan and Ambrose Burnside were reluctant to fight or were poor battlefield commanders. The Union faced a number of setbacks in the East but did achieve an important victory at the Battle of Antietam in September 1862. This battle stopped the Confederacy's first invasion of the North in the East. It also permitted Lincoln to issue the Emancipation Proclamation and make the ending of slavery one of the North's war aims.
Lincoln refused to end slavery during 1861 and the first half of 1862 for several reasons. First, he believed that the United States Constitution prevented the president from seizing the
property -- slaves -- of the country's citizens without due process. Second, Lincoln feared alienating the residents of the Border States -- slave states that had remained in the Union. These people included residents of Kentucky, Missouri, Delaware, and Maryland. If these people joined with the South, hundreds of thousands of more men could join the Confederate armies. Lincoln wanted to solidify the North's control over these slaveholding states before acting against slavery. Third, Lincoln realized that many white Southerners and Northerners would not support slavery's termination, because it might result in the equality for the African Americans with white people. Lincoln hoped to persuade prominent African-American leaders that the black population should move from the United States if slavery ended. The president also had to negotiate with other nations, to convince these countries to accept African-American immigrants. Finally, Lincoln worried that ending slavery would alienate any Unionist sympathizers currently in the South, further strengthening the Confederate war effort.
By the summer of 1862, Lincoln had become convinced that slavery had to end. Many of his concerns about ending the institution had been alleviated. Northern troops now had firm control over the Border States and they would be able to prevent these states from seceding from the United States. Southerners remained committed to the war effort. Lincoln was convinced that any Unionist support in the Confederacy could not succeed in persuading secessionists to rejoin the United States. A growing number of Northerners began to believe that slavery was morally wrong. As Northern soldiers marched into the South, many of these men saw the true brutality of slavery for the first time. Many of these men informed their loved ones in the North about the injustice of the institution. Finally, Lincoln believed that the federal government did have the right to hamper its enemy's ability to wage war. Slaves grew crops and produced other supplies for the Confederate military. The United States Constitution allowed the president to adopt measures during times of war to help guarantee a military victory. Lincoln decided that ending slavery would hamper the Confederate war effort and was legal under the United States Constitution. Lincoln drafted an initial copy of the Emancipation Proclamation in July 1862, but he did not issue it to the public until September 22, 1862. .