Why did Cuba intervene in Angola, and what effect did it have?

It was only after the MPLA debacle at Catengue that the Cubans became fully aware of the South African intervention, that Luanda would be taken and that their training missions were in grave danger unless they took immediate action. Neto had requested immediate and massive reinforcements from Havana at the urging of Argüelles. On 4 November Castro decided to launch an intervention on an unprecedented scale, codenaming the mission Operation Carlota, after 'Black Carlota', the leader of a slave rebellion in 1843.

there is no chart here so no one can answer this.

may i have the answer choices?