Question: What was the pro-slavery group called that Silas Soule clashed with?

Related documents: [0]  [DOC] Silas Stillman Soule (July 26, 1838 – April 23, 1865) was an American abolitionist, Kansas Territory Jayhawker, anti-slavery militant, and a friend of John Brown and Walt Whitman. Later, during the American Civil War, he joined the Colorado volunteers, rising to the rank of Captain in the Union Army. [END] 
[1]  [DOC] Jayhawkers is a term that came to prominence just before the American Civil War in Bleeding Kansas, where it was adopted by militant bands affiliated with the free-state cause. These bands, known as "Jayhawkers", were guerrilla fighters who often clashed with pro-slavery groups from Missouri known at the time as "Border Ruffians". After the Civil War, the word "Jayhawker" became synonymous with the people of Kansas. Today a modified version of the term, Jayhawk, is used as a nickname for a native-born Kansan, but more typically for a student, fan, or alumnus of the University of Kansas. [END]  
Answer: "Border Ruffians"
"Border Ruffians"