Upvote:2
Rome did not build defensive barriers on cities or provinces for hundreds of years. They relied on the Legions marching out onto the other sides' turf and breaking up opposition.
Cities without the ability to project force thousands of miles always have used walls. Even in a desert, there is rock or clay to build a defensive wall and ditch. Aside from a thin defensive perimeter around the walls, I know of no city that ever relied on the enemy getting deep inside and fighting in the houses. This does too much damage.
Upvote:2
Walls (or physical barriers) appear to be the standard defensive structure for a city in order to keep invaders out. Are there examples of cultures/cities that successfully defended themselves without the use of barriers, and how did they accomplish that?
Since the Napoleonic revolution in warfare, logistics have played a greater and greater role in the defence of cities. Walls play no significant role in the defence of cities from states, though they do play some role in the defence of settlements from nationalities (these conflicts are much much lower intensity than state warfare).
Are there examples of defensive tactics that relied on the attacker being within the city boundary?
The partisan commune (consider Warsaw, twice; or Budapest 1956) / "City Fighting" / "Urban Warfare" / Military Operations in Urban Terrain / Fighting in Built Up Areas
One aim of these tactics or operations in defence is to impose a higher cost on the opposing force than defending in non-urban terrain.
Upvote:2
Once the English stopped fighting each other, they relied on sea power for protection against continental enemies. For example: Hapsburg Spain. They would speak of their "wooden walls," meaning ships. This is only a partial example, but certainly the English relied less on fortifications than, say, the fought-over cities of the Low Countries.
Upvote:4
When at the peak of its power, ancient Sparta had no walls around its capital city. The standard cliche one reads and hears is that the "walls" of Sparta were the fighting men of its army.