According to Tacitus, 8,000 allied auxiliary infantry formed the centre, while 3,000 cavalry were on the flanks, with the Roman legionaries as a reserve in front of their camp.Duncan B. Campbell, Mons Graupius AD 83, Oxford: Osprey Publishing, 2010 Estimates for the size of the Roman army range from 17,000 to 30,000;Edwards, Kevin J; Ian Ralston Scotland After the Ice Age Polygon 24 January 2003 p.204 A temporary camp at Durno (20m or 32km NW of Aberdeen) covered 144 acres (60ha) and could have held 24,000 men. Roger J.A. Wilson A Guide to the Roman Remains in Britain 2002 Constable, London although Tacitus says that 11,000 auxiliaries were engaged, along with a further four squadrons of cavalry, the number of legionaries in reserve is uncertain. The Caledonian army, which Tacitus claims was led by Calgacus (but only mentions him as giving a speech, probably fictitious),Braund, David Ruling Roman Britain: Kings, Queens, Governors and Emperors from Julius Caesar to Agricola Routledge; 1 edition (5 Sep 1996) pp.8, 169Woolliscroft, D. J.; Hoffman, B. Rome's First Frontier; the Flavian Occupation of Northern Scotland Tempus (June 1, 2006) p.217 was said to be over 30,000 strong. It was stationed mostly on higher ground; its front ranks were on the level ground, but the other ranks rose in tiers, up the slope of the hill in a horseshoe formation. The Caledonian chariotry charged about on the level plain between the two armies.
