Complex sentence: At end of 1907 Wilson was transferred to the Indian Political Department and sent to the Persian Gulf where he served as a political officer, soldier and senior administrator until 1920, when he joined the Anglo-Persian Oil Company as resident director in the Gulf.
Split into simpler sentences: At end of 1907 Wilson was transferred to the Indian Political Department and sent to the Persian Gulf where he served as a political officer, soldier and senior administrator until 1920. In any event, he then joined the Anglo-Persian Oil Company as resident director in the Gulf.