Question

How did abraham lincoln ensure that border states supported the union?

Answer 1

To ensure border states remained in the union, he never said his goal was to end slavery, only that it was to save the union.

Answer 2

Abraham Lincoln insisted that his only goal was to save the union, not end slavery.

Lincoln's concern was to save the Union, instead of saving or destroying slavery. Lincoln would save the Union the shortest way he could under the Constitution and by using extra constitutional means. In other words, he aimed to save the Union at any cost, towards slavery.

Lincoln wrote a letter pertaining to the Union and slavery basically claiming that he believed that the Union could be saved without destroying slavery.