Bleeding Kansas: Pro-Slavery and Free-Soil Forces War

Armed conflict erupts in Kansas Territory throughout 1856 between pro-slavery "Border Ruffians" from Missouri and free-soil settlers. Pro-slavery men sack Lawrence on May 21. John Brown retaliates with the Pottawatomie massacre May 24-25. Over 200 people are killed in guerrilla fighting. The violence demonstrates that slavery cannot expand peacefully — the nation is heading toward war.