ABSTRACT
Environmental conditions generated a different military trajectory in the continents outside Eurasia. Most of the precolonial societies of North America, Central America, South America, Africa and Oceania remained at the level of Neolithic culture before the European conquest. Lack of draught animals and iron implements prevented agriculture in precolonial North America from crossing the threshold, as in Eurasia. Further, the arid climate and lack of navigable rivers also obstructed the development of intensive agriculture, trade and commerce in the south-western parts of North America. Mountains run along the west and east coasts of North Mexico. At the centre of Mexico, another mountain chain runs east to west, almost from coast to coast. The union of these three mountain ranges creates a vast highland region in Central Mexico characterised by mountains, well-watered valleys and a temperate climate.
