What is believed to be the main cause of the bantu migrations that contributed to growth in south africa?

They needed more land for a growing population.

Explanation:

The Bantu were an African group of people who spoke various dialects of the Bantu language. These people originally came from the area around the Niger River in southern West Africa. From this region, they expanded throughout central, eastern and southern Africa. They took their traditional practices, language and technology with them, influencing the whole continent. However, the precise dynamics of the migration, as well as the specific reasons for it are not well-known.

explanation:

japan participated in world war i from 1914 to 1918 in an alliance with entente powers and played an important role in securing the sea lanes in the west pacific and indian oceans against the imperial german navy as the member of the allies.

which time period is this? or is this story fictional, i'm going to need more info to answer this question