Around 1821 the Zulu general Mzilikazi of the Khumalo clan successfully rebelled against King Shaka and established his own clan, the Ndebele. The Ndebele fought their way northwards into the Transvaal, leaving a trail of destruction in their wake and beginning an era of widespread devastation known as the Mfecane. When Dutch trekboers converged on the Transvaal in 1836, they drove the tribe even further northward, with the assistance of Tswana Barolong warriors and Griqua commandos. By 1838 the Ndebele had conquered the Rozwi Empire, along with the other smaller Shona states, and reduced them to vassaldom.