Al-Sallal led the revolutionary forces that deposed King Muhammad al-Badr and brought the Mutawakkilite Kingdom of Yemen to an end. He presided over the newly founded Yemen Arab Republic (YAR), with close ties to Gamal Abdel Nasser of Egypt which served as the Yemen Arab Republic's strongest ally in the war against the Saudi Arabian-backed Mutawakkilite royalists that lasted into 1970.