Foreign enlistment in the American Civil War (1861–1865) reflected the conflict's international significance among both governments and their citizenry. Diplomatic and popular interest were aroused by the United States' status as a nascent power at the time, and by the war's central cause being the globally divisive issue of slavery. Consequently, many men enlisted from abroad and among immigrant communities in the U.S. When hostilities first broke out, roughly 13% of Americans were foreign-born, the vast majority concentrated in northern cities; subsequently, foreign enlistment largely favored the Union, which was also far more successful at attracting volunteers.