 Two months into his premiership , Smith was deeply offended when Whitehall informed him that , for the first time since 1932 , Southern Rhodesia would not be represented at the year 's Commonwealth Prime Ministers ' Conference as the decision had been taken to only include fully independent states in future . The quarrel over the terms for independence caused the Southern Rhodesian military 's traditional British and American suppliers to impose an informal embargo , and motivated Britain to cut off financial aid to Salisbury around the same time . The United States promptly followed suit . Political violence between the rival black nationalist movements in Rhodesia intensified during mid @-@ 1964 , leading to jail terms or preventive restriction for several prominent nationalists , and concurrent bans for their respective parties . When Northern Rhodesia became Zambia in October 1964 , Southern Rhodesia dropped " Southern " from its name , and initiated legislation to this effect , but Britain refused assent , saying that the colony could not legally rename itself . Salisbury continued using the shortened name anyway . 
