Final answer:
The motivating force behind President Lincoln's Gettysburg Address, Second Inaugural, and the decision to suspend the right of habeas corpus was the preservation of the Union.
Step-by-step explanation:
The motivating force behind President Lincoln's Gettysburg Address, Second Inaugural, and the decision to suspend the right of habeas corpus was the preservation of the Union. Although Lincoln detested slavery, his top priority was to preserve the Union and prevent the secession of the Southern states. The preservation of the Union was the primary goal that influenced his decisions and actions during the Civil War.