The underground railroad
How did it happen?

The Underground Railroad was a network of people, African American as well as white, offering shelter and aid to escaped enslaved people from the South. It developed as a convergence of several different clandestine efforts. The exact dates of its existence are not known, but it operated from the late 18th century to the Civil War, at which point its efforts continued to undermine the Confederacy in a less-secretive fashion. The Underground Railroad ceased operations about 1863, during the Civil War. In reality, its work moved aboveground as part of the Union effort against the Confederacy.

sumerians were responsible.

c) troops march forward in close formation against newer, more accurate weapons