Geology has controlled the outcome of battle since warfare began. Understanding the nature of ground, the opportunity for active defence and tunnelling, the ability to move freely across tracts of terrain, and the provision of natural resources are some of the problems that have faced armies for centuries. Peter Doyle specialises in the interpretation of historic terrain, and is a noted expert in the field having studied battles both in the USA (Revolutionary War, Apache Wars, Civil War) and Europe (Gallipoli, the Western Front, Arnhem, Battle of the Bulge).