Final answer:
Presidents Abraham Lincoln and Franklin D. Roosevelt both emphasized the need for national unity and the protection of founding principles during their respective times of war—the Civil War and World War II.
Step-by-step explanation:
Presidents Abraham Lincoln and Franklin D. Roosevelt both addressed the concept of war by calling for Americans to protect the founding principles of the nation. Lincoln, in his inaugural address, emphasized the permanent nature of the Union and affirmed the importance of majority rule, making a plea for reconciliation and unity. Roosevelt, in his time, encouraged Americans to work with him against the forces of the Great Depression, giving a wartime analogy and stating, "The only thing we have to fear is fear itself", to rally the nation's spirit for the forthcoming challenges of World War II.
Both presidents saw their respective conflicts—the Civil War and World War II—as times when the nation needed to come together to uphold and fight for its foundational values. They both emphasized unity and a collective effort in their approaches to leading the nation during wartime. Despite the differences in their circumstances, their core message of protecting the nation's principles and calling for unity in the face of adversity was strikingly similar.