In this task, you are given a question. You have to answer the question based on your information.
Q: John Brown, was an American abolitionist who believed and advocated that armed insurrection was the only way to overthrow the institution of slavery in the United States, Brown first gained attention when he led small groups of volunteers during which series of violent political confrontations in the United States between 1854 and 1861 involving anti-slavery "Free-Staters" and pro-slavery "Border Ruffian", or "southern" elements in Kansas?
A:
Bleeding Kansas