The terrain on the Advance Wars battlefield is more than just scenery; it significantly impacts unit movement, defense, and even vision. Roads offer fast movement but no defensive bonus. Plains provide a slight defensive bonus. Woods and Mountains offer significant defensive bonuses, making units harder to hit, but they also restrict movement. Rivers and Sea tiles are only traversable by specific unit types. Cities, Bases, and HQs provide defensive bonuses and, crucially, generate funds for your army.
Capturing properties like Cities and Factories is essential for economic superiority. Cities generate income each turn, allowing you to build more units. Factories (or 'Bases') allow you to produce ground units, while Ports produce naval units and Airports produce air units. Your HQ is your most vital property; if it's captured, you lose the game. Always consider terrain when planning attacks and defenses. Placing units on high-defense terrain can turn the tide of battle, while using roads for rapid deployment can secure objectives quickly.