Why did the Portuguese take so long to leave Angola?

My taking on the meaning of this question is why the Portuguese left much later than the other colonial powers in Africa. read more

Portuguese Angola was a territory covering 1,246,700 km², an area greater than France and Spain put together. It had 5,198 km of terrestrial borders and a coastline with 1,600 km. Its geography was diverse. read more

When the Portuguese refused to renew the agreement in 1853, the British ceased paying tariffs at the ports on either side of the Congo River mouth, claiming that Portugal's claim had expired because they had left the area unoccupied for too long. read more

All the Portuguese colonies in Africa are rapidly granted their independence. Portuguese Guinea is the first, in September 1974. Portuguese East Africa follows in June 1975, taking the new name Mozambique. The republic of Cape Verde is established in July. And Angola, in the middle of civil war, becomes independent in November 1975. read more