Ridwan ibn Walakhshi
... that in 1138–39, Fatimid vizier Ridwan ibn Walakhshi attempted to overthrow the Isma'ili caliphate and replace it with a Sunni regime headed by himself?
... that in 1138–39, <a href="./Vizier_(Fatimid_Caliphate)" id="mwCQM" rel="mw:WikiLink" title="Vizier (Fatimid Caliphate)">Fatimid vizier</a> <b id="mwCQQ"><a href="./Ridwan_ibn_Walakhshi" id="mwCQU" rel="mw:WikiLink" title="Ridwan ibn Walakhshi">Ridwan ibn Walakhshi</a></b> attempted to overthrow the <a href="./Isma'ilism" id="mwCQY" rel="mw:WikiLink" title="Isma'ilism">Isma'ili</a> caliphate and replace it with a <a href="./Sunni_Islam" id="mwCQc" rel="mw:WikiLink" title="Sunni Islam">Sunni</a> regime headed by himself?