On 11 November 1965 the white-minority government of the Rhodesia made a Unilateral Declartion of Independence. The primary cause of this was the United Kingdom unwilingness to consider full independence for the African state without a movement toward black majority rule. As we know, this was considered unacceptable to the white minority.
It is often speculated that the date chosen (Rememberance Day) was symbolic as the UDI government wanted Britons to remember the sacrificeof white Rhodesians in WW2. This was to attempt to dissuade the British govt from any attempt to intervene in the situation.
Unlike the case of South Africa, which despite the moral outrage against aparteid, there was no thougt that Sth Africa was any but a legitimate nation state. However Rhodesia could claim no such legitimacy (I believe that even Sth Africa refused to officially recognise it).
Although there was a minority opinion within the UK in support of British military intervention in the end, the UK took no such action, preferring diplomatic means and boycotts, etc.
Suppose instead that UK military intervention had gone ahead, with the goal of toppling the white Rhodesian govt and instead temporarily bringing Rhodesia back under British control until a transition to black-majority rule occurs.
What would be the effects of this?
What POD would this require? Perhaps the Left wing of the British Labour Party is more dominant, with it's more anti-imperialist stance dominant. How would the British Establishment react to this, as many right-wingers at the time perceived black independence movements as communist-inspired terrorist organisations? Taking into account of course, that British PM Harold Wilson was already regarded with significant suspicion by many members of the establishment.
How would the USA and USSR react?
Would the intervention of British troops cause a morale collapse among white Rhodesians leading to a quick surrender or would it be a drawn-out battle.
How would South Africa react? Would they decide to sit on the sidelines, not wanting to risk direct confrontation with the UK? Or would they view a successful intervention as too much of a risk to aparteid in Sth Africa and intervene in support of white Rhodesians?
Finally, how this change the relationship between black Zimbabweans today with the West. Assuming they continue to have a distrust and hatred of white Zimbabweans, due to the war, might they have a more positive attitude towards the UK and the West, sort of view them as helping their liberation? If so this would dramatically alter Zimbabwean politics, as Robert Mugage would't be able to rely on anti-Western sentiment during the past 20 or so years?