American nationalism
According to Adam Goodheart, the modern meaning of the American flag, and the reverence of many Americans towards it, was forged by Major Robert Anderson's fight in defense of the flag at the Battle of Fort Sumter, which opened the American Civil War in April 1861. During the war the flag was used throughout the Union to symbolize American nationalism and rejection of secessionism. Goodheart explains the flag was transformed into a sacred symbol of patriotism: