Superior Resources: The Union had a larger population, more industrial capacity, and a more efficient transportation system than the Confederacy. This allowed them to mobilize and equip a larger army, produce more weapons and supplies, and transport troops and supplies more quickly and efficiently.
Leadership: The Union was led by President Abraham Lincoln, a skilled politician and leader, and generals such as Ulysses S. Grant and William T. Sherman, who proved to be effective military strategists. The Confederacy, on the other hand, had a more decentralized and less effective government and military leadership.
Strategy: The Union adopted a strategy of total war, aiming to destroy the Confederacy's economy, infrastructure, and military forces. This included campaigns to capture key cities and transportation hubs, such as Atlanta and Vicksburg, as well as naval blockades to prevent the Confederacy from importing supplies.
Diplomacy: The Union was able to gain support from other countries, including Great Britain and France, which prevented the Confederacy from gaining international recognition and support.
Internal Dissent: The Confederacy faced internal dissent and divisions, particularly in the later stages of the war. There was growing opposition to the war, especially among non-slaveholding whites and enslaved people, who saw little benefit in fighting for the preservation of slavery.
Technological Advancements: The Union took advantage of technological advancements such as the telegraph, which allowed for faster communication between military units, and the rifled musket, which gave Union soldiers a significant advantage in firepower over Confederate troops.
Emancipation: The Union's decision to issue the Emancipation Proclamation in 1863 not only helped to boost morale among Union troops and gain support for the war effort, but also weakened the Confederacy by depriving them of a significant portion of their labor force and eroding their international support.
The combination of these factors ultimately contributed to the Union victory in the Civil War and the preservation of the United States as a single nation.