McPherson discusses Lincoln’s role as commander in chief, which, despite Lincoln’s lack of military experience at the beginning of his presidency, is central to his place in history. McPherson is critical of the turn to social history at the expense of military history, and he asserts that the social interpretation favored from the 1960s forward cannot be fully understood without including the lens of military history.

McPherson outlines and defines the five functions that the commander in chief oversees. Lincoln’s policy—the political aims of the nation in war—was to preserve the one indivisible nation and democratic republic conceived in 1776. Lincoln’s national strategy, or the mobilization of resources to achieve war aims, was to appoint prominent political and ethnic leaders to high military ranks, and he also focused on the conciliation of border states and anti-abolitionist Northern Democrats by keeping emancipation off the table. By 1862, Lincoln’s national strategy shifted to stipulating further professional military criteria for the ranks of brigadier general or general. He also increased his focus on emancipation, and this decision activated the Northern abolitionist majority and the manpower of formerly enslaved Black people.

Concerning military strategy, or the use of armed forces, Lincoln was forced to take a more active approach than any other presidents.