Agricola was governor of the Roman Province of Britannia for 7 years from 77 to 84. The book describes the Roman war machine. It then argues that Vespasian decided in 71 to conquer the whole of the island of Britain, and substantially expanded the army and sent three of his best generals to complete the conquest. The opposing commanders and the order of battle of the Exercitus Britannia are analysed. The heart of the book is a year by year analysis of Agricola's 7 campaigns, unlocking his strategic intent in each year and his subtle exploitation of terrain and his celtic allies. This section includes a new revolutionary typology of Roman forts based on their size and location. In addition to successfully occupying North Wales, Pennines, Lowlands and Scotland; the it is proposed that Agricola made a reconnaissance to Ireland in 81. Finally the consequences of Agricola's campaigns and what could have happened if Agricola's conquests had been consolidated rather than let go by Domitian, are analysed.