What new challenge does Lincoln face that his fifteen predecessors have not?

In 1864, Lincoln faced many challenges to his presidency. The war was now in its fourth year, and many were questioning if the South could ever be fully conquered militarily. Union General Ulysses S. Grant mounted a massive campaign in the spring of that year to finally defeat the Confederate army of General Robert E. Lee, but after sustaining significant losses at the Wilderness, Spotsylvania, and Cold Harbor, the Yankees bogged down around Petersburg, Virginia. As the fall approached, Grant seemed no closer to defeating Lee than his predecessors. Additionally, Union General William T. Sherman was planted outside of Atlanta, but he could not take that city. Some of the Radical Republicans were unhappy with Lincoln’s conciliatory plan for reconstruction of the South. And many Northerners had never been happy with Lincoln’s 1862 Emancipation Proclamation, which converted the war from one of reunion to a crusade to destroy slavery. Weariness with the war fueled calls for a compromise with the seceded states.

Explanation:

the term is einsatzgruppen