Final answer:
Lincoln's appointment of Grant as commander of all Union forces signaled the adoption of a policy of total war and unconditional surrender, aiming to expedite the end of the Civil War through a relentless campaign.
Step-by-step explanation:
When President Abraham Lincoln gave Ulysses S. Grant command of all Union forces, he was adopting a policy of total war and unconditional surrender. Under Grant's stern leadership, the Union army pursued a relentless campaign across multiple fronts, aiming to crush the Confederate’s ability to continue fighting. This approach marked a significant shift from the previous more cautious policies and involved striking at both military and civilian resources to undermine the Confederates’ will to fight, thus hastening the end of the war.
Grant's strategy included recruiting freed slaves into the Union Army as emphasized by Lincoln, a move which bolstered troop numbers and significantly contributed to Union war victories. With Grant’s command and the adoption of a total war policy, Lincoln sought to break the Confederate resistance and enforce the Union's terms, leading to a turning point in the Civil War.