 Complete the following phrase:  Dunsterville was assigned to re-inforce the defence of the key oil-field and port of Baku in present-day Azerbaijan, held from 26 July 1918 by the anti-Soviet Centro Caspian Dictatorship. Dunsterforce personnel first arrived in Baku on 6 August 1918. However, the British and their allies had to abandon Baku on 14 September 1918 in the face of an onslaught by 14,000 Ottoman troops, who 