Final answer:
Texas settlers had a geographic advantage in their knowledge of the local terrain and support from the civilian population, which were pivotal in their victory over the Mexican Army during the Texas Revolution.
Step-by-step explanation:
The geographic advantage that Texas settlers had over the Mexican Army was largely due to their familiarity with the local terrain, bolstered by the support of the civilian population in their efforts to defend their territory. Settlers in Texas, also known as Texans, maintained a cultural distinction from the Mexican population, the tejanos, and formed local governments which they dominated. The significant presence of American settlers who were at odds with Mexican laws, such as the abolition of slavery, coupled with the settlers' experience with firearms and understanding of the local geography, provided a strategic advantage during conflicts like the Texas Revolution.
In the Runaway Scrape, fleeing the Revolution following defeats like those at Goliad and the Alamo, the Texan army, commanded by Sam Houston, eventually defeated the larger army of Santa Anna at the Battle of San Jacinto. This victory was attributed to Houston's ability to take the Mexican forces by surprise, a feat that likely benefited from his knowledge of the terrain. The issue of borders also heavily influenced the conflict, with Texas and Mexico disputing over the Rio Grande and the Nueces River as the rightful boundary.