 "The present emperor being a fool" (according to English Ambassador Sir Thomas Roe), he was compared unfavorably with his predecessor.In fact, it was his mother Halime Sultan the de facto-co-ruler as Valide Sultan of the Ottoman empire.Political instability was generated by conflict between the Janissaries and the sipahis (Ottoman cavalry), followed by the Abaza rebellion, which occurred when the governor-general of Erzurum, Abaza Mehmed Pasha, decided to march to Istanbul to avenge the murder of Osman II.