Which war was primarily sparked by issues surrounding slavery in the United States?

The American Civil War was primarily sparked by issues surrounding slavery in the United States. The conflict emerged from a long-standing controversy over the institution of slavery, particularly its expansion into newly acquired territories and states. The deep-seated differences between the Northern states, which were generally opposed to slavery, and the Southern states, which depended on an agricultural economy reliant on slave labor, led to increasing tensions.

The election of Abraham Lincoln in 1860, who was seen as an opponent of the spread of slavery, prompted several Southern states to secede from the Union, ultimately leading to the war. Key events, such as the Missouri Compromise and the Dred Scott decision, further fueled disputes that highlighted the moral and economic divides between free and slave states.

In contrast, the other wars listed—World War I, the Revolutionary War, and World War II—were driven by different issues: World War I was rooted in alliances and imperial ambitions, the Revolutionary War was about colonial independence from Britain and issues of governance, and World War II was largely sparked by fascism and global aggression. Thus, the American Civil War stands out specifically for its direct connection to the contentious issue of slavery.