During the Heian period, although the Onosaki clan was treated as the hereditary vassal of Satake clan since Michimori ONOSAKI and Michinaga ONOSAKI who were the head family of Onosaki clan had been serving the Satake clan, Onosaki clan established the position as a senior vassal of Satake clan in the 'Battle of Satake'.
平安期、小野崎氏宗家の小野崎通盛・小野崎通長が佐竹氏に臣従して以来、小野崎氏は佐竹氏の譜代家臣として遇されてきたが、小野崎氏が佐竹氏の重臣としての地位を確立した戦いが「佐竹の乱」である。