Complex sentence: The Great Trek was used by Afrikaner nationalists as a core symbol of a common Afrikaans history in an effort to promote the idea of an Afrikaans nation in a narrative that promoted the ideals of the National Party.
Split into simpler sentences: The Great Trek was used by Afrikaner nationalists as a core symbol of a common Afrikaans history. It was done in a way that promoted the idea of an Afrikaans nation and in a narrative that promoted the ideals of the National Party.