Complex sentence: Powles 1928, pp.71--72 Each regiment was divided into three groups, the first group leaving at the 17:30 19 December, followed by the second smaller group at 21:35.
Split into simpler sentences: Powles 1928, pp.71--72 Each regiment was divided into three groups, the first group leaving on the 19 December. Followed by the second smaller group at 21:35.