alliances with other Indian tribes, but that too was useless because the Seminoles had destroyed all the other Indians when they entered Florida in the late eighteenth century. The U.S. Army fought and won the Mexican–American War (1846–1848), which was a defining event for both countries. The U.S. victory resulted in acquisition of territory that eventually became all or parts of the states of California, Nevada, Utah, Colorado, Arizona, Wyoming and New Mexico. American Civil War The American Civil War was the costliest war for the U.S. in terms of casualties. After most slave states, located in the southern U.S., formed the Confederate States, the Confederate States Army, led by former U.S. Army officers, mobilized a large fraction of Southern white manpower. Forces of the United States (the "Union" or "the North") formed the Union Army, consisting of a small body of regular army units and a large body of volunteer units raised from every state, north and south, except South Carolina. For the first two years, Confederate forces did well in set battles but lost control of the border states. The Confederates had the advantage of defending a large territory in an area where disease caused twice as many deaths as combat. The Union pursued a strategy of seizing the coastline, blockading the ports, and taking control of the river systems. By 1863, the Confederacy was being strangled. Its eastern armies fought well, but the western armies were defeated one after another until the Union forces captured New Orleans in 1862 along with the Tennessee River. In the Vicksburg Campaign of 1862–1863, General Ulysses Grant seized the Mississippi River and cut off the Southwest. Grant took command of Union forces in 1864 and after a series of battles with very heavy casualties, he had General Robert E. Lee under siege in Richmond as General William T. Sherman captured Atlanta and marched through Georgia and the Carolinas. The Confederate capital was abandoned in April 1865 and Lee subsequently surrendered his army at Appomattox Court House. All other Confederate armies surrendered within a few months. The war remains the deadliest conflict in U.S. history, resulting in the deaths of 620,000 men on both sides. Based on 1860 census figures, 8% of all white males aged 13 to 43 died in the war, including 6.4% in the North and 18% in the South. Later 19th century Following the Civil War, the U.S.