The Redlegs were a group of soldiers/vigilantes who had the task of protecting Kansas from the invasion and influence of pro-slave Missouri during the American civil war. They were organized by Jim Lane, a US Senator from Kansas and were initially funded by and had the approval of the US Government. As their guerilla attacks and atrocities against anyone who sympathized with the south became more viscious, the government support was withdrawn.
The Redlegs were so named because of the dyed leather or sheepskin leggings they wore. The group was an offspring of the notorious jayhawks who had a reputation of dealing harshly and usually fatally with anyone who they suspected supported slavery or the south. The US Government dealt with this group (the jayhawks) by inscripting them into the ranks of the Union Army. The Redlegs, however moved in the opposite direction, having started with government support and losing it.
The Redlegs terrorized the area of the Kansas/Missouri border, killing often and seemingly at random. In an interview with Mary Ethel Noland, the first cousin of Harry S Truman, she says: "sometimes the Kansas Redlegs would come over and they would shoot a harmless old man because he was a Southern sympathizer, or sometimes they would even hang one; and sometimes they would shoot a young boy who was almost too young to bear arms, but they would trump up excuses because they were really a band of desperados, not real soldiers." The main thing that kept the Redlegs somewhat in check was a running battle with "Quantrill's Raiders," a small squad of Confederate partisans led by William Clark Quantrill, who harassed Union soldiers and sympathizers along the Kansas-Missouri border and often clashed with jayhawkers, and Redlegs. Quantrill was considered an outlaw by union forces, but regarded as a hero and protector by frightened southern sympathizers in the area.
In the movie The Outlaw Josey Wales it was a band of renegade Redlegs who killed Josey Wales' family and burned his farm in the opening scene. The Redlegs are remembered more favorably, however, among some, and there are even sports teams named after them.