Complex sentence: After a brief career in law, Buchan simultaneously began writing and his political and diplomatic career, serving as a private secretary to the colonial administrator of various colonies in Southern Africa, and eventually wrote propaganda for the British war effort in First World War.
Split into simpler sentences: After a brief legal career Buchan simultaneously began both his writing career and his political and diplomatic career, serving as a private secretary to the colonial administrator of various colonies in Southern Africa. He eventually wrote propaganda for the British war effort in the First World War.