Military geography is a sub-field of geography that is used by the military, as well as academics and politicians, to understand the geopolitical sphere through the military lens. To accomplish these ends, military geographers consider topics from geopolitics to physical locations’ influences on military operations and the cultural and economic impacts of a military presence. On a tactical level, a military geographer might put together the terrain and the drainage system below the surface, so a unit is not at a disadvantage if the enemy uses the drainage system to ambush it, especially in urban warfare.