Simplify the following text for a Grade 8 native English-speaking person.
Original: With Namibia 's independence from South African administration in 1990 , Windhoek was recognized as the capital city of South-West Africa as administered by the South African government .
Simplified: During World War I , Windhoek was captured by South Africa . It was the capital of South West Africa ( Namibia ) under South African control until the independence of Namibia in 1990 .