Terrain that limits mobility, such as forests and mountains, can be used as a force multiplier by the smaller force and as a force inhibitor against the larger force, especially one operating far from its logistical base. Such terrain is called difficult terrain. Urban areas, though generally having good transport access, provide innumerable ready-made defensible positions with easy escape routes, and can also become difficult terrain if prolonged combat fills the streets with rubble. An early example of terrain advantage is the Battle of Thermopylae, 480 BC, where the narrow terrain of a defile was used to funnel the Persian forces, who were numerically superior, to a point where they could not use their size as an advantage. In 12th century, irregulars known as the Assassins were successful in the Nizari Ismaili state. The "state" consisted of fortresses (such as the Alamut Castle) built on strategic mountaintops and highlands with difficult access, surrounded by hostile lands. The Assassins developed tactics to eliminate high-value targets that posed a threat to their security, including the Crusaders. In the American Revolutionary War, Patriot Lieutenant Colonel Francis Marion, known as the "Swamp Fox", took advantage of irregular tactics, interior lines, and the wilderness of colonial South Carolina to stymie larger British regular forces. Yugoslav Partisans, starting as small detachments around mountain villages in 1941, fought the German and other Axis occupation forces, successfully taking advantage of the rough terrain to survive despite their small numbers. Over the next four years, they slowly forced their enemies back, recovering population centers and resources, eventually growing into the regular Yugoslav Army. Role of civilians Civilians can play an important role in determining the outcome of an asymmetric war. In such conflicts, when it is easy for insurgents to quickly assimilate into the population after an attack, tips on the timing or location of insurgent activity can greatly undermine the resistance. An information-centric framework, in which civilians are seen primarily as sources of strategic information rather than resources, provides a paradigm to better understand the dynamics of such conflicts where civilian information-sharing is important. The framework assumes that: The consequential action of noncombatants (civilians) is information sharing, rather than supplying resources, recruits, or shelter to combatants. Information can be shared anonymously, without endangering the civilian who relays it. Given the additional assumption that the larger or dominant force is the government, the framework suggests the following implications: Civilians