Complex sentence: By on 18 August, most of the contingent had been evacuated to Aden but HMAS "Hobart" and the HQ stayed behind until morning before sailing and the Italians entered Berbera on the evening of 19 August.
Split into simpler sentences: By on 18 August, most of the contingent had been evacuated to Aden but HMAS "Hobart" and the HQ stayed behind until morning before sailing. The Italians entered Berbera on the evening of 19 August.