Complex sentence: He had effectively been superseded before then; on 20 December 1965, Smith named Dupont as "Officer Administering the Government"; an earlier attempt to have him named as Governor-General of Rhodesia was dismissed out of hand.
Split into simpler sentences: He had effectively been superseded before then; on 20 December 1965, Smith named Dupont as "Officer Administering the Government". An earlier attempt to have Dupont named as Governor-General of Rhodesia had been dismissed out of hand.