Complex sentence: Much of his military service was spent in British South Africa, previously he was Commissioner of Police of the Metropolis, the head of the London Metropolitan Police from 1886 to 1888, during the period of the Jack the Ripper murders.
Split into simpler sentences: Much of his military service was spent in British South Africa. Previously he was police chief, the head of the London Metropolitan Police from 1886 to 1888, during the period of the Jack the Ripper murders.