Final answer:
The Civil War signified a historic pivot by significantly increasing the federal government's power at the expense of states' rights, culminating in the Union's victory which supported a strong central government and the implementation of the Fourteenth and Fifteenth Amendments. The post-war period introduced dual federalism but maintained the supremacy of the national government through Supreme Court decisions.
Step-by-step explanation:
The Civil War can be seen as "a historic pivot in the role of federal power" because it significantly increased the federal government's power relative to the states. This shift occurred as both the Union and the Confederacy mobilized resources and personnel to a degree never seen before in American history, which set new precedents for federal authority. Women's mobilization also played a significant role, demonstrating the nationwide effort demanded by the war.
The ideological divide over state versus federal power was stark before the war, especially regarding the issue of slavery. The Southern states favored a weaker central government to protect their slave-based economy, while the North supported a stronger federal government that could override state laws and ultimately abolish slavery. The Civil War's outcome resolved these power struggles chiefly through military might and later through legal frameworks.
Impact on federalism after the war was profound. The Union victory affirmed the national government's supremacy over the states. It ended any future considerations of secession and forced the former Confederate states to comply with federal mandates, including the ratification of the Fourteenth and Fifteenth Amendments, which radically altered the balance of power in favor of the national government.
The concept of dual federalism emerged post-war as a new phase of U.S. federalism, distinguishing more clearly the jurisdictions of the state versus the national government. However, the Supreme Court continued to resolve the remaining power struggles, usually in favor of strengthening national authority.
In summary, the Civil War was a key moment in American history that shifted political power towards a dominant federal government, influencing the economic, social, and political fabric of the nation. The post-war developments marked a new era in federal-state relations and set a precedent for federal dominance in policy and governance.