Complex sentence: He undertook service as an army physician at the Battle of Waterloo (1815), in England and during the Cape Frontier War (1819) in southern Africa, before he settled in his home town of Edinburgh from 1820.
Split into simpler sentences: He undertook service as an army physician at the Battle of Waterloo in 1815 in England and during the Cape Frontier War (1819) in southern Africa. He eventually settled in his home town of Edinburgh from 1820.