The British government of Harold Wilson condemned the move as illegal, as did the Commonwealth and the United Nations, which moved to impose sanctions on the rebel colony.
The apartheid regime in South Africa continued to give economic support to Rhodesia, but did not extend official recognition to the new state. Portugal, then the colonial power in neighbouring Mozambique, gave economic support, including access to Mozambique's sea ports, but following the change of regime in Lisbon, Mozambique became independent under the Marxist Frelimo regime of Samora Machel. This was a severe blow to the Smith regime, militarily as well as economically, as Machel was an ally of Robert Mugabe and allowed ZANU a base there to mount incursions into Rhodesia.
Smith sought to make Rhodesia a dominion, with Queen Elizabeth II as head of state, but the governor, Sir Humphrey Gibbs, refused to recognise Smith's authority. Smith responded by appointing a government minister, Clifford Dupont, as "Officer Administrating the Government". However, in order to distance Rhodesia from its colonial master, Smith declared Rhodesia a republic in 1970, with Dupont as the first President, and Sir Humphrey was made to leave the country. It was hoped that by severing constitutional links with Britain, the country would end any ambiguity about its status, gain diplomatic recognition, and economic sanctions would cease, but this did not materialise.
A new national flag was adopted in 1968 to replace the British colonial ensign, but Rhodesia had no national anthem until 1974, when it adopted one called Rise O Voices of Rhodesia, to the tune of the Ode to Joy of Beethoven's Ninth Symphony. Following the declaration of a republic in 1970, the following words were written, but no tune was ever composed:
In 1978, an Internal Settlement was signed between the Smith regime, and the African nationalist parties, the United African National Council (UANC), led by Bishop Abel Muzorewa, and ZANU Ndonga, led by Ndabaningi Sithole. However, this did not involve the two main parties in exile, Zimbabwe African National Union - Patriotic Front (ZANU PF) led by Robert Mugabe and the Zimbabwe African People's Union (ZAPU), led by the late Joshua Nkomo. Consequently, it was rejected by the international community.
In April 1979, the first multiracial elections were held in Rhodesia, which saw Abel Muzorewa become the first black Prime Minister of what was now called Zimbabwe Rhodesia. However, under the Internal Settlement, whites retained control of the country's judiciary, civil service, police and armed forces, as well as having a quarter of the seats in parliament reserved for them. While this was welcomed by the British government of Margaret Thatcher, opposition from the rest of the Commonwealth, meant that Britain did not recognise the new state.
In December 1979, following multi-party talks at Lancaster House in London, Britain resumed control of the rebel colony, and with the help of observers from other Commonwealth countries, saw the first free elections. The Republic of Zimbabwe came into being on April 18, 1980.