Final answer:
President Lincoln moved cautiously toward emancipation for several reasons: preserving the Union, the political landscape, and the legal limitations of his presidential powers. He waited to avoid escalating secessionist tensions and sought to maintain his campaign promises until strategic considerations and congressional pressure necessitated a move toward ending slavery with the Emancipation Proclamation.
Step-by-step explanation:
Abraham Lincoln was personally opposed to slavery but did not end it immediately upon becoming President for several complex reasons. First and foremost, Lincoln's primary concern was to maintain the Union's cohesion and find a way to bring the Southern states back without them seceding. He did not interfere with slavery initially, as stated during his campaign, to avoid provoking the South and because he believed that the Southern papers would misrepresent his position, undermining any public statements he could make.
Moreover, before his inauguration, various individuals proposed compromises, like the Crittenden Compromise, to recognize slavery in all territories south of the Missouri Compromise line. Lincoln refused these as they went against the Republican Party's core principle of preventing slavery's expansion into new territories. Therefore, the compromises and propositions presented before his presidency were rejected.
Additionally, Lincoln moved cautiously toward emancipation. By July, considering military, political, and diplomatic reasons, such as weakening the Confederates' ability to sustain their war effort and preventing British support for the Confederacy, Lincoln decided it was the right time to make a move towards ending slavery. These considerations, alongside the gradually increasing pressure from Republicans in Congress and the reality of the war, led Lincoln to issue the Emancipation Proclamation on September 22, 1862, after the Confederate retreat at Antietam, with an effective date of January 1, 1863.
It's also important to note that Lincoln did not have the constitutional legal right to end slavery across the states; it required constitutional amendments and the eventual ratification of the 13th Amendment in December 1865 after his death.