Final answer:
The Texas Rangers likely turned back due to the uncertain and dangerous military situation following the Texas Revolution where conflicts such as the Alamo and the Goliad defeat triggered a widespread retreat and strategic withdrawal, known as the Runaway Scrape, amidst ongoing disputes over Texas's independence and its border.
Step-by-step explanation:
The Texas Rangers turned back after trying to go from San Antonio to El Paso during a time of great political and military upheaval in the wake of the Texas Revolution. The Texas Revolution saw heavy losses for the Texan forces with the defeats at Goliad and the Alamo, sparking the Runaway Scrape, where civilians and military alike fled from the advancing army of Santa Anna. This exodus included not just Tejanos but all factions in the revolution.
The tide turned at the Battle of San Jacinto where Sam Houston's forces captured Santa Anna and forced him to sign the Treaty of Velasco, temporarily ending hostilities without granting recognition of the Republic by Mexico. However, the troubles were far from over as Santa Anna, upon his return to Mexico City, denounced the private treaty claiming duress, and Mexico continued to view Texas as a renegade province, leading to ongoing tensions and potential conflict on the uncertain border marked by the Rio Grande and the Nueces River.
These events contribute to the understanding of why the Texas Rangers may have had to turn back. The military situation, motivations for independence, and concern for territory and safety would all have been factors influencing their movements during this volatile time as the "Texas problem" remained unresolved.