In 1856 Brown, four of his sons and three other followers killed five unarmed men and boys in retaliation for a raid by Missouri Border Ruffians on the town of Lawrence, Kansas. It was called the Pottawatomie massacre and it marked the beginning of the period called Bleeding Kansas. On August 30, 1856, Brown and about 40 men fought against about 250–300 Border Ruffians at the Battle of Osawatomie. Two years later Brown and his men raided into Missouri where they killed a planter and set 11 slaves free. They also took wagons, horses and mules.