You must mean the “Northern War of Aggression”
The American Civil War was fought in the United States from 1861 to 1865. After a long standing controversy over slavery and state’s rights, war broke out in April, 1861, when Confederates attacked Fort Sumter in South Carolina, shortly after Abraham Lincoln was elected. The Union faced secessionists in eleven Southern states grouped together as the Confederate States of America. The Union won the war, which remains the bloodiest in U.S. history.
Among the 34 U.S. states in February 1861, seven Southern slave states individually declared their secession from the U.S. to form the Confederate States of America. The Confederacy grew to include eleven states; it claimed two more border states (Kentucky and Missouri), the Indian Territory, and the southern portions of the western territories of Arizona and New Mexico, which was organized and incorporated into the Confederacy as Confederate Arizona. The Confederacy was never diplomatically recognized by the United States government, nor was it recognized by any foreign country (although some countries such as Britain and France recognized it as a belligerent power). The states that remained loyal, including the border states where slavery was legal, were known as the Union or the North. The war ended with the surrender of all the Confederate armies and the dissolution of the Confederate government in the spring of 1865.
The Union won the war when General Robert E. Lee surrendered to General Ulysses S. Grant at the battle of Appomattox, which triggered a series of surrenders by Confederate generals throughout the southern states. Four years of intense combat left 620,000 to 750,000 soldiers dead, a higher number than the number of American military deaths in World War I and World War II combined, and much of the South’s infrastructure was destroyed. The Confederacy collapsed and 4 million slaves were freed (most of them by Lincoln’s Emancipation Proclamation). The Reconstruction Era (1863–1877) overlapped and followed the war, with the process of restoring national unity, strengthening the national government, and granting civil rights to freed slaves throughout the country.