Alex Magaisa, former adviser to Zimbabwean opposition leader Morgan Tsvangirai, told the BBC: “They have decided not to call it a coup because they know that a coup does not sell, it will be condemned.
“But as far as authority is concerned it seems very clear that President Mugabe is now just a president in name and authority is now residing in the military.”
Zanu-PF had accused Gen Chiwenga of “treasonable conduct” after he issued his warning that the army might intervene.
What was the political situation before the army acted?
Last month, Mrs Mugabe accused allies of Mr Mnangagwa of planning a coup.
Grace Mugabe is seen as a potential successor to her elderly husband.
Gen Chiwenga is a close ally of Mr Mnangagwa and both are veterans of the 1970s war which ended white minority rule.
The leader of the war veterans, Chris Mutsvangwa, welcomed the military move, telling Reuters: “This is a correction of a state that was careening off the cliff.
“It’s the end of a very painful and sad chapter in the history of a young nation, in which a dictator, as he became old, surrendered his court to a gang of thieves around his wife.”